Positions for conceiving

Does anybody know if being on top when your man ejaculates greatly lowers possibility of conception? I've read both sides where some say missionary or doggie style are best, and others say there has been no proof that position makes any difference. My husband likes for me to be on top when he ejaculates....I always turn over on my back right after and put a pillow under my hips or put my legs up on the headboard trying to defy gravity. Sometimes he even turns over with me and pushes it in more just to make sure it stays. No matter how long I stay there , it all always seems to come back out when I stand up. I know it only takes one sperm, and most of what comes out is just seminal fluid from what ive read, but I get so paranoid in thinking that it's not getting to where it needs to go and it's all for nothing. I blame everything on my age too(I'm 42, about to turn 43 in Nov.) In thinking that my body struggles more. Anybody else my age gotten pregnant being on top? Or can anybody offer some helpful, encouraging, and even truthful words in this matter? Does the position even matter? Or am I thinking and worrying about it too much? Thanks a bunch.