I have to disagree with some of the things @drhat77 is saying.
The pills are not really a high dose of hormones. They’re a pretty low dose of synthetic versions of estrogen and progesterone with a much higher binding affinity than endogenous hormones. So if you measure your hormone levels while you’re taking the pill, you actually have far, far less (almost zero) estrogen and progesterone than a naturally cycling woman.
In naturally cycling women, changes in estrogen and progesterone across the cycle trigger a surge of luteinizing hormone and follicle stimulating hormone. These hormones instruct the ovary to release a mature ovum. Since estrogen and progesterone are held at a constant, low level in women on the pill, the egg never matures and is never released.
To answer your specific questions, you will be on a 28 day cycle. Many women experience breakthrough bleeding, especially in the first few months on the pill—this should go away, but if it doesn’t, you can try a different pill.
The periods that you have are not real periods. They are breakthrough bleeding caused by the lack of synthetic hormones. (If you keep taking the pills indefinitely, you will not have a period indefinitely.)
Mood changes are also a common side effect. These might go away with time. They might not. Again, you can always try another pill.
If you have more questions definitely post back. My lab is gearing up to launch several projects looking at the effects of hormonal contraception on cognition, so it’s something I am always happy to talk about.