Is it okay to have sex 4 weeks PP?

So I don’t have any blood but I have a lot of thick cervical mucus. I had a c section and I had a check up at two weeks and they said everything looked good and I was supposed to have a 6 week check up but they just to wait until 12 weeks so they can put my IUD in at the same visit. I had a fever right after delivery so they assumed I had an infection and they said they can do IUD’s before 12 weeks post infection.