You may be worrying too much. Yes the thought of any std is scary, thats why its so important to try to get to know someone first now days. But condoms, when used correctly are 98% effective. If you are still doubt their reliability try pairing them with a spermicide to avoid pregnancy. Unfortunately the std thing is much more complicated. You can go to your local health dept. For an std test, just to be sure, and honestly, there's nothing wrong with having one at least once a year if you're going to have multiple partners. Good luck.
How Effective Are Condoms, When Used Properly, In Preventing The Transmission Of HIV? And Are Swollen Lymph Nodes In The Groin, Along With Normal Cold Symptoms, A Sign That I Should Get Tested, Or Just Have A Cold?
According to amfAR, The American Foundation for AIDS Research, "When male condoms are used correctly and consistently, they are 80-95% effective in reducing the risk of HIV infection." amFar: "The Effectiveness of Condoms in Preventing HIV Transmission"