I discovered the exact same thing 2 weeks PP. I panicked and went to have it checked and the physio said it was normal after just having a baby. She used an u/s to make sure I was doing my PFE correctly (which I wasn't.. Apparently I was pushing down instead of pulling up! WTF!?) and she told me to come back at 6 weeks PP. By then everything had gone back to normal. My sister and my mum told me they had exactly the same thing happen. So please don't panic like I did! Obviously get it checked at your 6 week check, keep doing your PFE even if it feels like it's not working.