Hi and welcome to the forums!
Well, FCEGM’s post pretty much says it all and I completely concur. It’s just wrong.
There are a lot of ancient practices that have been repackaged in modern society as fun or intriguing harmless things. But they can be spiritually dangerous and offensive to God. (Yoga is another practice that Christians should have no part of, yet it has been presented to unsuspecting Christians as something that is good for you. The physical aspect may feel good, the spiritual aspect is a slap in the face to Jesus Christ as yoga is rooted in Hindu worship of other gods. But I digress.) Anyhow, now that you have seen the CCC for yourself, I’m hoping that you will resist the temptation to look up your horoscope. I’m always one to recommend the Sacrament of Reconcilliation if you have sinned, so I will do so now. However, since it appears you did not know any better, you would not be in a state of mortal sin over this matter. However, now you do know better so your culpability would change if you keep on with it.
I know there will be some Catholic posters who will disagree with me and chalk it all up to harmless fun. But it only takes a "harmless’ little thing like this for the devil to get a toehold. Once you get hooked on horoscopes, you could then start watching the psychics on TV and getting further from the Truth of Christ (devil now getting a foothold), then you could go a step further and get into New Age religion, seances, ouija boards, etc. I say this only with love and respect and am not implying that you are spiritually weak and would go that far… but it does happen. Too often.