I started my period July 7th and then again this month a just started July 25th!. I don't know why?. is it a sign I could be pregnant?. please help!

Sounds like you could be just having an off month. Every once in a while we may skip a period, or have 2 periods in one month. I would doubt you are pregnant if you are having periods.

It does not mean that you are pregnant. Lack of a period is. Contact your obgyn and have some blood drawn for test to check hormone and thyroid levels.

Well I have had sexual intercourse after my real period and then I have another one?. I have been really sick also such as, headache, stomach ache, diareahea and nausea!. it just doesn't make sense

The first sign of pregnancy is a missed period.