It could be one of several things--Most likely:
1.) Ovulation
2.) Implantation
3.) Ovarian cysts
My guess (by my personal history), is YES, it's too soon to tell. Most HPTs don't show up positive until at least 5-8 weeks of pregnancy. Not a fun fact when you're wanting to be pregnant and wanting to know NOW if you are or not.
Don't give up hope...and try to relax. Stress doesn't make for a good environment if you're trying to conceive...and it won't change anything one way or the other this month. Only time will tell. I suggest waiting another 2 weeks before expecting a HPT to show positive.
Best wishes!