What would you think of me touching myself while sharing a bed with someone, multiple times?
Why did you want to touch yourself?
I just felt horny, I can't control my feelings
Well is this person your partner? If so, that is okay, but if they're not, masturbating around them would be invasive to the other person. You might be making them super uncomfortable if someone next to them was touching themselves like that.
I don't care. It feels good after a long day.
You need to care, as doing that with somebody else in bed with you who isn't your partner would make them see you in a negative light since they didn't give you permission. You could get a bad reputation with others if you keep doing that.
Masturbation when you don't have a consenting partner is something that you should take care of in private instead.