Periods and Hinduism

Since childhood I was always taught to stay away from the temples, religious events, etc during menstrual cycle. The thing is I never understood what the reasoning behind this is. I would really appreciate all the explanation I can get, not only that but like the religious rules that go along with this side of a woman's life in Hinduism.

Another thing is with it ganpati season I normally celebrate ganpati in a grand way however the past two years have been extremely disappointing. The reason is because last year my periods were in the way so I didn't celebrate ganpati at all. This year I started my periods on the 24th and normal 5 day cycle would end on the 29th. However I tend to go over board at least a day or two. So my mom said since it had already been my 5th day I can still celebrate ganpati. So I decided to schedule the pooja for sunday. I went shopping today after taking a shower. Bought all the mithais and everything only to come home and realize my periods are still on. So then I told my mom that they can eat everything I will just go and buy new mithai and fruits and all. She said no it's okay since it had already been my 5th day. However I grew up with my nana nani and they were extremely strict about it. So I obviously feel the same way. So in this situation I don't know whether to side with my mom or go by what I feel.

Periods and Hinduism