after sex can be from one of several different sources. First, bleeding anytime after or not associated with sex could be coming from your uterus. If you had sex near when you were expecting to get your period, this could be just an early sign that you are about to start your cycle. Likewise you if you take birth control
pills, this could be breath through bleeding that sometimes occurs. The other possible source of your bleeding is your vaginal wall. Bleeding from the vaginal wall can occur when you have sex with inadequate lubrication. It sounds like this is a possibility in you. This is usually associated with some significant pain during and after sex. The final possible source of your bleeding is from your cervix. The cervix contains blood vessels that can break occasionally during sex. Since you said that your cervix feels a bit swollen, this is could be the source of your bleeding.
The best thing for you to do is to schedule an appointment with your primary care doctor
or OBGYN, whoever you feel more comfortable seeing about this issue. Your doctor will want to perform a pelvic exam to look for any ongoing bleeding that you may have. Good luck.