Orgasm ???

So my boyfriend wants to eat me out and we’ve never done anything like that before. I’ve never orgasmed and I think this might cause me to have one. I’ve never pleasured myself, I’ve only ever been fingered once but not for long. I don’t know what it feels like to orgasm or to cum, but one time I was having a night to myself and I think I might have came close but I had to stop because I thought I was going to pee. Is it similar to a pee feeling? How do you prevent yourself from peeing?