help!! weird lump

hi! I dont know where to go. I've been experiencing severe period pain and bleeding to the point where I throw up, its only started in the past like 4 months or so (the pain, I've always had a heavy flow). I have a doctor's appointment next week where I'm going to get recommended to a specialist. I have a weird lump on the left side of my bellybutton, not crazy obvious and its soft, but i can tell when i stick my belly out at all and it hasn't been there before. I'm 16 and I'm so terrified, I'm so scared of cysts or cancer or anything like that. does anyone possibly know what it could be? also I havent been diagnosed with anything before, including endo, I'm just coming here because I dont know where else people could help me.