I feel like I'm having chemical pregnancies every month!!!

Hi, im 23 years old and I havent been necessarily trying to concieve but I havent been trying to prevent it either. For the past years my period has always been regular but I used to get bad cramps. They stopped for about a year until 2 months ago (March 19, day 2 of my period that month) I got cramps so bad I couldnt walk standing straight up. I ended up missing work and in the emergency room because I was passing clots the size of my pinky finger. I had noticed my period was acting funny that month because I was spotting pink for 3 days prior to the pain starting and the actual menstruation beginning... so I took a test before it started and it was negative. the next day in the hospital the doctor also gave me a test which was still negative of course they ruled out a miscarriage. Gave me two different ultrasounds and a pap smear and found nothing, not even a cyst. My period last month came on April 15 and again I spotted pink for 3 days prior to the flow actually starting and this time i had ZERO PAIN, not even the slightest cramp, no bloating, no tender nipples nothing none of the normal pms symptoms i would get every month. I could barely even tell I was on my period. And on top that I bled so heavy that month that it went off in like 2 1/2 days when it usually lasts about 5 with a extra day of spotting. This month i started spotting about 4 days ago while my period is not supposed to be due for another couple of days. I started wearing a pantyliner thinking my period was on its way but nope not even enough to fill up a pantyliner let alone soil it at all. I would only see the pink spotting when I wipe. For 4 days I've been going thru this until today I started cramping slightly and the red blood started coming still not enough to fill a tampon but the cramps were normal yet I still havent been able to even fill a tampon after hours. Nipples still not sore but I did get heavily nauseous the day the spotting started. I guess I have my period now but the flow is no where near normal.I have no clue what this could be, every where that I look up pink spotting is saying implantation bleeding but I end up getting my period. I know this is normal for some women to spot before their period but I never have. This started happening 2 months ago and im worried. What could causing this?? My cycle is off too ive always been a 28 day cycle but lately it will go from 28 to 30 and then drop to 27 i can't chart anything cause none of it adds up anymore. If anyone has been through this please help, its eating me alive feeling like I might be miscarrying month after month. And please ask questions if I left any important details out...