Should i wait to take my diet pills?

I been sick for weeks. One point of time I couldn't even lay on either side nor my stomach. my period was on the 30th and it was short. Now that I'm not heavy nauseated or in pain I'm constant hungry all the time. Whatever I eat isn't enough. I get headaches when I dont eat. My boyfriend thinks I'm pregnant but I don't. I'm convinced I'm not. My appetite has picked up