I agree with the comment that it could be low blood sugar. - But keep taking your vitamins. They contain Magnesium which is very important to your well-being.
I just looked at your profile and saw that you're 19, at that age you won't get breast cancer and the breast tissue is actually too dense to even get an mammogram
I can tell you for a fact this has nothing to do with vitamins. Put this into perspective, people can go months without eating. The issue is anxiety. As for the lumps in your chest, that's probably causing you anxiety and medically speaking, unless you're in your 40s or 50s, they are nothing to worry about. Breast lumps are normal and represent calcification as a result of minor trauma such as from running.
I would say this has nothing to do with the vitamins.
How many calories are you eating in a day?
Sounds more like a blood sugar issue or it could be related to anxiety.....not sure.