You didn't say whether or not there was an odor or itching and irritation. It could be a yeast infection. You can get a test kit for it at any drug store without a prescription. If it is a yeast infection, you can buy the medication for it without a prescription at the drug store or any department store in the feminine hygiene aisle.
Wearing a tampon when you are not having your period makes the environment warmer and more humid and only encourages the growth of yeast. Whenever possible, don't use a tampon and allow that area to 'breathe.' You should also wear cotton underwear to help get over an infection.

but there is no itching or erritation. not really an odor either. just the goo

Ask your mom to take you to the doctor. No, this is not because you had sex. The doctor visit will be kept private (at least if you live in the U.S., I'm not sure about other countries, check on that). You can tell the doctor anything and he or she cannot tell you mom.

At the very least, you should start getting gynecological exams after you have sex and you can get birth control, as well.

I don't think it's anything serious, but since it's bothering you so much, go to the doctor.

If there is not itching, irritation or odor, it's probably normal vaginal discharge. Sometimes it's white other times it is clear. This discharge is especially heavy right before or after your period.
I think you should stop wearing the tampons because doing so can cause an overgrowth of yeast. Wear pantyliners and change them several times a day.