I had unprotected sex with my husband 18 days ago, we have been trying to conceive for 6 months now. I'm getting negative hpt, do u think there is a chance that I could be pregnant this time around?

You take a HPT 18 days or less after the incident.. and expect it to be accurate?

At 18 days you are pushing it for getting a reliable result... if you wait until its been 4 weeks you can trust the results you get from a HPT.

You can not test 18 days after sex, it will show negative. You have to wait @ 4 to 5 weeks after sex and normally a week to two week after the next missed period.