If you had unprotected sex, its possible you are pregnant. The only way to find out is with a test (a blood or urine test). Typically, the over the counter tests will give you a positive result 2 weeks after possible conception so if you did get pregnant 3 weeks ago you would get a positive result now (even though you haven missed your period - you can still test now). Liquid coming out of your breast when you squeeze it can be quite normal and not pregnancy related - in fact, it wouldnt be related to pregnancy so early into it.
If you have been getting "really bad" stomach pains it is important to find out whether you are pregnant or not because severe stomach pain while pregnant can signify an ectopic pregnancy which requires immediate medical treatment. Of course, stomach pain is common during pregnancy and in those that arent pregnant but its important to find out where you stand and rule such things out.
You said you are scared to test. Are you scared because you want to get pregnant and dont want a negative result or because you dont want to get pregnant? Either way, a 5 min test will give you the results.