just a question

I have a weird question... I feel like I'm pregnant. If I am, it's been a while, like 18 weeks!! Of course I've done pregnancy tests, they were negative. Also a blood test at the GP was negative. Still, the feeling won't let go. According to the doctor, it's impossible for me to be pregnant if both tests are negative. I do have all sorts of ailments and my belly is starting to show... last week I had a smear test done because the GP didn't see a reason to wait. Can they see anything regarding pregnancy after the smear test, and could the GP have seen/felt something during the smear test (e.g., position of the uterus or something)? I already have two kids, so I know what the feeling of being pregnant is like. It's not like we're actively trying for a third child. Does anyone relate????
ps. posted under "wanting children" because I didn't know where else to put it