My husband and I both watch a fair amount of porn.  Sometimes together sometimes separate.  Sometimes because one/both of us is horny and wants to get off, sometimes out of boredom.  It's not uncommon for us to be sitting/lying next to each other with one of us watching TV while the other gets himself off to porn.  Lets face it, no matter how talented your partner is, your longest sexual relationship is with yourself.  Sometimes you just want an orgasm, not sex.  A helping hand (so to speak) while appreciated, sometimes gets in the way. 

Do you absolutely have to have a dildo?  I mean a sex toy that is obviously a fake penis.  I know that the visual appeal and the risk of getting caught with it are a turn on, but if all you want is something to shove in your ass then I suggest that you take advantage of any number of household items.  When I was younger, closeted, and lived with my parents I used anything I could get my hands on.  A non-lubricated condom (so there was no residual lube left behind on the item INSIDE the condom) plus any slick substance I could lay my hands on got me off many times.  anything long and hard was a potential toy.  Hairbrush handle, toilet plunger handle, even a water bottle.  As long as it wouldn't rip through the condom because of rough/sharp edges and I could keep hold of it so I didn't lose it up my ass, I tried it at least once.  If my parents found the condoms, I'd have been embarrassed (at that age) but not outed.  Lube would have been assumed to be for jerking off, again embarrassing for a teen but "better" than the alternative (or so I thought at the time).  If you don't have a sex toy, you don't have to hide a sex toy.  All you need is something innocuous that you can USE as sex toy.

Hope this helps,
Guncle (Gay Uncle) RJ