I am on seasonique birth control and I have been for a month and a half. I had sex about 3 to 4 weeks ago and lately I have had headaches, white mucusy discharge, I've gained 8 pounds, my breast are sore and have grown a lot, plus, I'm sometimes nausios. I took a couple of pregnancy texts a week or to ago and they were negative, but I still can help but think I am.
this is urgent, please give me your best adive
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You may be experiencing side effects of the birth control. I have included some information on this for you.
Some of the common side effects of birth control pills include but are not limited to:

Breakthrough bleeding and spotting between periods
Nausea and vomiting
Bloating
Breast tenderness and enlargement
Changes in your eyes that make it more difficult to wear contact lenses
Headaches
Acne
Changes in sex drive

You can also gain weight on birth control.
I would talk with your physician. He/She may want to change what you are on, and may want to do a blood test to see if you are pregnant. I would probably think this is a side effect issue though.