Sex issue 😕

DH and I were both in the mood last night, after no sex for about 4 weeks. Prior to this, it's felt great every time. Last night though it just felt swollen, couldn't get all the way in without it hurting and just didn't feel good 😕 almost 37 weeks. I felt so disappointed in myself, any tips? Maybe some lube, even though it wasn't really needed. Or just wait it out?