Please help in convincing my boss?

Hi, someone please help me in convincing my bosses. Both my bosses are ladies. Lately I have been suffering from urinary problems. I've been taking sick leaves very often now. My bosses think I'm lying to �skip from work. I told them that I am having severe stomach problems. Now my doctor refers me to see a urologist and I don't seem to convince my bosses for getting another sick leave. I am really worried that I would loose my job if I take one more sick Leave this month as I have taken 4 leave already. How should I convince them? This would have been easier if my bosses were men.�