If you are having sex, then of course there is a chance you could be pregnant! No method of birth control is 100% effective, so that means any time you have sex, you could get pregnant. However, if you're not even taking your pills like you're supposed to, then obviously that will increase your chances of getting pregnant.
You could try testing now. If you are negative, but still have the symptoms in a week or two, try testing again.
If you don't want to get pregnant, you'll have to take your pills every day at the same time, or not have sex, or switch to a form of birth control that does not require you to take something every day such as condoms, the patch, etc.