What Causes Light And Short Periods While Suffering From PCOS?

I was diagnosed with PCOS about 2 years ago. My periods have always been off and on, however back in 2016, around October, my periods began to come every month. They were pretty regular. Until January, when I started my period on the 22nd, and it ended on the 26th. It was a normal period. It is currently July 17th, and I haven t had a period since. About 2 months after my last period, I began to bleed. It was very light and only lasted about a day and a half. I have never had a period that light that only lasted a day or so. I didn t worry tho because I wasn t have any other symptoms of pregnancy. Until about 2 months ago when I began to feel like my stomach was getting kind of big. I hadn t made any changes that made me gain weight, so I started to pay attention. Now, my stomach is obviously bigger, but not huge. And it s very hard. I can feel my skin and a layer of fat (I m not a skinny girl lol) and then directly below there is something there. I have been taking pregnancy tests since my missed period and they all have come back negative. I get frequent headaches, often feel like I m gonna throw up, but never do, and that s about it. I don t know what to do. I know I should go to the hospital but I don t want to go make a fool of myself. But either way, why is my stomach so hard????