What's wrong with me???

Ok so, before high school I got my period on the dot every month at the exact same time. Well starting high school I started to get a little off. Well I'm 20 years old now I can go without my period for about 3 months? My mom does some homeopathic medications. Well she looked up that "angelic root" is suppose to help regulate your cycle. Well every single time I have used it I get my period 3 days after I take the pill. But if I
Don't take it, like I said I can go months without having my period. Now I am sexually active, I've been with the same guy for 5 years and we've only been sexually active for 3 years. I haven't taken any pregnancy tests. But I'm just wondering why I am so irregular...