If you have an ectopic pregnancy?

I don't think I'm pregnant, as I'm not cycling yet since my last baby (Breastfeeding), but I've been having some sharp pain in my left side over near my ovary and last week I had some red/pink spotting for a day or two. I don't want to buy an HPT if it won't help me rule out ectopic pregnancy. I'm thinking it is probably a cyst, but I want to be sure.

Thanks!