Haven't breastfed in 3 mo, no period.

Hi all, My son was born October of 2016. I breastfed him for 4 months at which point I stopped (I gradually weaned for 10 days leading up to my last day of breastfeeding). After I stopped I expected to get my period pretty quickly. It's been 13 weeks and nothing. I'm worried that something is going on, had blood drawn today but won't hear back till next week. To clarify, I am NOT pregnant! I was underweight before I was pregnant and I'm at my prepregnancy weight now. My bmi is right around 17.5 but my body composition is not different. Before pregnancy I did cardio and no weights but now I do a lot more weights and have increased my protein so I am more muscular. If I squeeze my nipples a little clearish liquid will come out. Is it normal to not have a period come back for this long?