Having frequent headaches, feeling bloated and can't eat. What's wrong?

Lately I have been having headache’s for almost the whole day and I have been tired too (sometimes I’m already kinda exhausted from walking up the stairs). I feel bloated like the whole day, and I can’t eat anything because the smell of food just makes me nauseous. After a few bites I’m done, and I’ve already lost a couple of pounds the past weeks. What’s wrong with me, I have never felt like this before and now I’m starting to worry a little bit.