When I began dating my XBF, he was large enough that he would actually tear me. I had bleeding wounds after we had sex. I hadn't been having regular sex at that point and I wasn't "stretching" enough.

I ended up waiting for the wounds to heal completely, going to a sex therapist to learn how to relax, and using artificial lube until I "got used to it".

The new BF is more manageable for me... :-)