First I had thrush, then a cold sore and now there are bumps on the back of my tongue. I've never had sex before but could it be HIV?

Paranoia. No. HIV does not just appear. And your symptoms are not in any way signs of such an infection. Every single patient who has come to he about bumps on their tongue are pointing at their taste buds. .
No. Unless you had intravenous drug use or other high risk behavior you do not have HIV. The bumps on the back of your tongue are taste buds, Cold sores are a common occurrence in normal people. If you are over the thrush, it is not an issue.