No Periods Since 3 Months, Bloating, Lower Abdominal Pains, Difficulty In Passing Stools. Pregnancy Test Negative. Possible Ovarian Cysts?

I am 21 years old. Sexually active with the same partner. My periods are irregular but are usually a wk to two wks late. I haven't had a period since valentines day. So I haven't had a period in 3mths. I went to the doctor 4 days ago n they send my blood test to the lab. My pt came back negative. So I'm not pregnant. I been bloated for the past 2 months, tender breasts and I recently have been having lower abdomen pains on my right side. The pains are everyday for the past two wks. Have trouble sleeping bc I only am able to sleep in prone position. I have trouble having bowel movements. The harder I try the more pressure I have on my tummy nd feel heavy after half hr trying. I am able to urine just fine but I get so frustrated with not being able to use #2 I have an appointment soon for an ultrasound bc they think I have a cyst on my ovaries but I fear worse..What's wrong with me?