Brown spotting, late period, neg. HPT, pregnant?

My husband & I have been married for 5 years and now we want kids. Last month we tried to conceive with my estimated ovulation dates (my reg. period cycle is 34 days). 1 week passed my period due date so I took a HPT & resulted with a neg. The day I tested, I noticed brown spotting on my underwear. I began to wear panty liners & now it's been 17 days past my period due date with 9 days of spotting in a row (some days light pinkish strips). I don't know what this could be. I've never had spotting for this long before. Plus I've noticed I smell things differently & my breasts are not tender as they usually are right before I start my period. From my knowledge, implantation occurs only once for a short period of time. Could it happen that implantation can occur for a long period of time & that I'm experiencing implantation? I'm afraid to take another HPT again because I don't want to see a neg. result. I've been wanting a baby for 2 years & now my husband is finally ready too. Any ideas? Thanks in advance.