Periods

I'm a bit worried about my periods I had a period back in December but then did not have one last month I've done three pregnancy tests they have all came back negative then I am late this month. 

In the last month I have nearly doubled in weight I am really hormonal I was on the pill when I feel pregnant last year and I had put on weight from the pill then the pregnancy then all that weight came off I wouldn't have put weight on for no reason and be hormonal and really sore I am practically shitting my self can some one PLEASE give me some advice