Thanks for the advice everyone… I still have the feeling that something is going on, and that I should trust my instinct.
We haven't had sex in a long time, he's always busy and away for work all day, often goes to birthday parties and such and "forgets his phone in the car".... The problem is that I can't directly ask him because he will immediately direct the attention to me and act defensive ("I think you are the one who's cheating"... "I've always been unsure of you.." etc)
I caught a glimpse of his phone password, and I need to catch a moment when he's in the shower or something to take a look.

We have been together for a few years and we love each other, and we have amazing sex. We live in different cities, but quite close, a one hour drive. We met on a sex date, but he's always been putting on an act like he's a saint who did an exception for me, whereas I am generally more open about sex and gay life in general.
A few months into our relationship I  caught him hiding a secret gay dating profile that he thought I wouldn't find out about… of course, he had an unbelievable excuse that I didn't buy for a second, but I let it slide because I didn't think he actually met anyone. When I confronted him about it, he claimed it was innocent, and he only had the profile active because he was sure I was cheating on him, so he needed somebody to talk to online, to give him advice  :cheesy2:
About a year later he picked up an STD after a holiday with friends, but in all honesty, it could be something that either of us had been dragging on for years, before we had even met, so I let that slide too. (nothing too serious, we both had it taken care of)
But I've always had a sneaking suspicion he's a pathological liar and a cheater... He has the perfect opportunity to cheat because we don't live together, so he has enough free time that is "unaccounted" for.
In the beginning of the relationship, I would find condoms in the most bizarre places that made no sense, and that we never needed there. (his work bag, his gym bag, the car...). He claimed they had been there for years and he had never used them, he carried them "just in case". I rolled my eyes and let it slide.
I also noticed he keeps an eye on a few guys on social media, and I have a feeling he's making his presence known in case he ever gets a chance to meet them... both the same type physically, totally different from me.
The problem is that I can't talk to him about it because he would just get defensive and spin things like it was me who was cheating, and he's the victim who's putting up with it. And of course, if I am imagining things, I don't want to accuse him of something I have no proof of.
I am considering taking a look into his phone, as bad as I would feel about doing it.
I love the guy, he loves me, he is an amazing partner, I just have a gut feeling he's hiding something. Maybe I'm just being paranoid because things are too good to be true?
What do I do?

could be two things:

medications

excessive jerking off to porn

Hi guys,
thanks for all your answers. Just wanted to make it clear that I have no intention on cheating on the boyfriend.
But I am really torn between my single lifestyle and the loving relationship. 

Hi, I have a problem and I don't know who to talk to.
I am currently in a committed loving relationship with a wonderful sexy guy whom I love very much.
Before meeting him I was quite promiscuous (but playing it safe, and STD free) and I really enjoyed my sexual lifestyle. I enjoyed hooking up with different guys and it was a big part of my life and personality.
I fell in love with one of my hookups and we started a serious monogamous relationship. Our sex life is amazing, he's the best sex I've ever had, but I feel "trapped" (for the lack of a better word) because I miss my sexual past and I feel like I haven't fulfilled all my wild sexual fantasies. I am almost addicted to porn because it allows me to fantasize without acting out on the fantasies. I would never cheat on my bf and talking about this is impossible because it would hurt his feelings. I just can't keep my sexual fantasies under control and it's all I think about 24/7.
Not sure what kind of support or help I am asking for here, but I had nowhehere else to turn to  :cheesy2:

definitely not
But I wouldn't mind being a str8 woman once per month to fuck all the hot str8 guys  >:D

I am close to my dad and he was supportive of me when I came out, I feel so lucky and blessed!

I have a beard and I am attracted to bearded guys…. in my experience, beards are attracted to beards

I would says definitely the face, but the situation with my boyfriend was almost opposite… he definitely has a handsome face, but his dick is his best asset, and I was more impressed by the dick than anything else physically

not sure if this makes me shallow, or just proves the point that size does matter - but as a top I have never been into dicks, but I met a guy with the most perfect beautiful big dick and he turned me into a versatile size queen  :cheesy2: