I had unprotected sex probably 3 to 4 weeks ago the day after my last menstrual cycle, I am supposed to start my next one in about 4 to 5 days. I was not on birth control at that time but am now, I am very bloated, have had cramps in my stomach, lower back pains, fever, and haven't been able to sleep and this has been going on for a few weeks now. Could someone help me out, I don't know whether to take a test before I am supposed to start my period, or should I wait a few days?

There are pregnancy tests that can detect if you are pregnant a week before your period.

Does it sound like I need to take one, and if so what's the brand?

I would recommend ClearBlue. You can't ever be sure why you are not feeling well, but if you take a test at least you won't have to worry till you get your period.