how do you know if u got endo?

I have been trying to get pregnant since late 2014 just had a HSG which was great results no blocked tubes and no issues. Been on Metformin since April 16 and will be taking clomid in next couple of months !! Is there a chance I have endo ? I'm so worried about what I have wrong with me !! Use to get painful periods but since I been on the Metformin I haven't had painful periods plus I ovulate all on my own so why can't I get pregnant !!!? Pls help