Period is late and took test still negative

My last period was Jan 4, 2017. On Feb 28 I took a clear blue test and it was negative. It was cycle day 56. Today I feel very nausea and have been getting regular cramps and pelvic pain. I also today had a headache.

Couple of weeks ago I did take another test and it was kind of positive. It was faint but it was there. So I don't know what is going on. Could I have been pregnant but I lost it or maybe I'm not that far along as I thought.

I still don't have my period yet at cycle day 57.

I do have 2 kids already boy 5yrs old and girl 2yrs old. I'm 28 yrs old and engaged to fiance.