Too much sex?

I'm 18 years old and have had sex with 6 different people, starting at 15 when I lost my virginity, I feel ashamed about it, is this too much for my age? I don't plan on sleeping with any other people for a long long time. I'm afraid and have been staling away at getting tested because I am so afraid, the times I did, they weren't always safe. Please send your advice, I will greatly appreciate any of it.