Pain and discomfort at 36 weeks having sex!

So pretty much my whole pregnancy I wasn't a fan of having sex at all.. I did it pretty much just to please my fiancée. Anyway, yesterday my doctor told me I can induce labor by having sex and his ejaculating in me. So now I want to for that reason. We tried yesterday, but I feel like he's shoving a tree inside me. And it's not the problem of me being dry because I'm not at all, I'm actually very wet, but I just feel SO tight and I feel like he's ripping me apart, I had to tell him to stop. So not only am I annoyed with the fact we can't have sex, I'm also terrified that I will tear unbelievably when I actually give birth since I clearly can't even handle his penis size, how the hell am I going to handle a baby coming out ??!