I recently had unprotected sex on 4/8/07. It tuned out that I ovulated on 4/10/07. I have 25 day average cycle length. I started having signs that could be pregnacny or PMS. I haven't been feeling well so I take a hpt 4/25/07and results were negative. My period came on the next day but it was lighter, more like spotting and it was light red. The question is could I still be pregnant ?

Highly unlikely that you are pregnant, but take another test in a week and you will soon find out.

You can always take another HPT, but it would probably be best to make an appointment at a health clinic or with a doctor to take another pregnancy test-- if for no other reason, to set your mind at ease. (A clinic will also have free or super-cheap condoms.) Stress can affect your cycle, which can cause more stress!
I'm not an expert by any means, but this is the advice I'd give my sister or daughter, if asked...