I want to try anal but I'm afraid my boyfriend will prefer it to vaginal?

Yeah, cause he will....

Another opinion: Anal sex is just another variation of sexual behavior. Just like oral sex and the 64 positions of Kama-Sutra. One does not perform just one activity. Each has it's advantages and emotions with it. There are times when vaginal sex and the various positions are fine. Other times the unique feelings of anal sex are enjoyed. Done right, anal sex can be a exciting alternative as long as the guy goes slowly, using fingers and plenty of lube, and time for the anal spincters to relax before he inserts his penis. The very first insertion may not feel good, but as you relax and start to enjoy it, you will find yourself pushing against your partner for more. If the guy does it wrong and too quickly, you will never again want anal sex again.