Anal sex is low risk for pregnancy, but it bears repeating that it's more risky from an STD standpoint. Condoms and lube should be used at all times, and you should never switch from anal to vaginal without putting on a clean condom. And there's a tiny risk of semen running down into the vagina.
Not trying to be rude, but where are you from?
Aside from all the clinical advice you've received, I would throw in some of the more obvious things, like trying oral or anal sex. The risk with these are minimal, probable less than 2%.
Hi Spin, You seem to me to be in the bigest dilemma going, your someone who really wants to have sex, But its the 2% thats getting in the way, so if you that affraid then its time to look at the BC pill, but please keep away from depo shot, if you think you are still worried add in some spermicide, but you may need to find the right one as some can affect you vagina. So still got your head in the sex cloud, theres not a lot more advice going.
Good Luck
If you are that afraid of pregnancy, you shouldnt have sex because the purpose of sex is to reproduce.
If you use it correctly, it's unlikely to break. This means pinching the tip when it goes on the penis and not using any sort of oil as lubricant. You need water based or silicone based lubricants to be safe. Oil degrades latex and makes it more likely to fail. The condom should not be expired, and should not have been stored in a really warm environment (they recommend not keeping them in your back pocket for this reason). When putting on the condom, make sure it will unroll the right way. If you put it on the wrong way and then flip it, there could be sperm from precum on it and there's a slight chance you could get pregnant.
If you're really worried, go to an ob/gyn clinic (they have free or sliding scale teen clinics in a lot of places if you don't want your parents to know). You can talk to them about birth control methods, and they might give you the pill. With the pill taken properly + condoms used properly, your chances of pregnancy are basically nil. But plenty of couples use condoms as their only source of birth control and do fine.