I need help

On April 3rd I got my period it came super early my cycle was only 20 days usually it is 30 i didn't think much of it thought it might just be stress. On May 4th I got period again but it was very light. but lately I have been extremely tired and nauseS very nauseS. My belly has grown and I'm usually pretty skinny I havent been eating more than usual but I do get cravings. I feel like I'm going crazy because I feel like there's bubbles poping in my belly and I get cramps I don't know to explain it. I've taken a pregnancy test but it came it out negative. Am I just going crazy or should I see a doctor???