We tried at 4 weeks, 5 weeks, and 6 weeks... It hurt. Honestly, it's only recently gotten better, and bubb is 5 months tomorrow. I had a 1st degree tear on the top and bottom, and it burned on the outside no matter how much lube we used. Inside felt ok once he got all the way in, but I couldn't handle his head going in and out.
We got one of those packs of lube that are for him and her, and that is what has helped me the most. I kinda don't ever want to have sex again without it, it feels sooo good!
My first post-partum period ended yesterday and I'm a cup user. I noticed it was a little irritating to insert and stung a little to remove. I was told before on this site that it really takes six months to be fully recovered.
I also want to throw in that I used a diaphragm before and after pregnancy. I was fitted at my six week appointment and I was the same size as pre-pregnancy. So if anyone has doubts about their size after, you may have nothing to worry about. I've also noticed no difference with how my cups fit, either.