Ok So I Am A 24 Year Old Woman With

Ok so I am a 24 year old woman with a history or irregular periods and ovarian cysts. For the past half year my periods have become more regular but now i havnt had a period since mid febuary and my stomach has been hurting quite a bit lately. Ive taking pregnancy test after pregnancy test and all have been negative. im really concerned for my health but i do not have a medical card and no income at the moment. Could i have another ovarian cyst? Could i be pregnant and the test just isnt working? I ask this second question because i have been pregnant before and have lost them (twins) because i didn't know, the tests i had taken all said negative. What should i do i dont want a repeat of that but how can i prevent it if i dont know? -Amelia