Pregnant?

My next period is 20 days away and my last period was just 4 days of brown I barely even had to wear a pad. Ive been on the pill since June and always have had a fuller flow. I've had a small weight gain, awful headaches and touches of nausea or just feeling an upset stomach at random times. I don't really keep track of sexual activity with my husband but it isn't all the time maybe once or twice a week. I'm on a birth control pill and if there is a chance I'm pregnant I don't want to do any harm to the baby.

Should I test or just wait it out? I can't tell if these are true symptoms or if I'm just not feeling the best with the weather changing. I've never had a chance of pregnancy so I don't really know what I'm experiencing