Best Position for First Time???

it’s my second year of college and I’ve been with my boyfriend for about 7 months now and we haven’t done much except making out and heavy petting. We haven’t taken “that” step yet.

He’s had sex before and I’m happy he’s been really understanding and patient with me. We talked about it and I said I was scared of the pain that it’ll hurt. I’ve masturbated a lot but even then it feels uncomfortable to put my fingers inside. I know for sure he’s much bigger than my fingers so it stops me from taking that step. Plus I wanted to do something special for his birthday coming up next week. What’s better than dinner, a movie and good ole’ birthday sex

So my question is: what position is best during your first time? Like is on top best or missionary or whatever seems fit to be more comfortable for me and him.