If you are over a month late, you would be about 8 weeks pregnant and would certainly test positive on a HPT - a blood test would detect HCG at this time too.
Well, blood tests are really accurate (even if your last 3 pregnancies took a long time to detect your hcg levels, blood tests will tell if they're rising or above average), so you're probably not pregnant - if you think you're pregnant though, you will make yourself believe you have symptoms. It took me and my husband 3 months to get pregnant and every month up until I got pregnant I thought I had every symptom, and I wasn't pregnant, then the month that I was I didn't have any symptoms! Check back with your doctor and continue hpt's if you really think you are pregnant though.