All Moms,My stomach is hard post parturm is this normal?

My husband and I had unprotected sex 3 weeks after my first born my stomach felt so saggy at the time I had the implant inserted 4 days after birth and exclusively breast fed around that time,and been sexually active ever since unprotected,the implant is said to be 99.9% accurate and I don't use condoms with my hubby,its been almost 4 weeks now my stomach feels hard and I'm still spotting..im gagging most of the time and slight cramps I know I can't base symptoms on a hard stomach but I'm scared to ask the question that I might be pregnant again,its impossible right?