Thick brown vaginal discharge and missed period?

I've been reading quite a bit on this site to try and find an answer to my question, and I've gotten a few ideas on what might be wrong with me, but I'd like to make my own post and see what sort of answers I get.

I'm 18 years old, and I've been having...

this irregular thick dark brown vaginal discharge every now and then, which sometimes will be accompanied with light pink blood. I can't remember when I last had my period, as I admit I don't regularly keep track of this like I should. But it's been a few months at least. I figured it could possibly be from stress as I've just gotten my first job recently, also I have been taking Lexapro (an anxiety/depression medicine) for a few weeks now, as well as a generic prescription medicine for Protonix (medicine for acid reflux/stomach ulcers). I don't know if these medicines have anything to do with the discharge or not.

Also, I do have unprotected as well as protected sex with my boyfriend of over 2 years. Never has he ejaculated in me during unprotected sex, and normally does not stay in for very long due to fear of pregnancy. Neither of us have ever been with any other partners and have never had any previous signs or symptoms of an STD or infections.

I am naturally a very stressed person and I know that can delay periods, but I haven't ever had this problem with the discharge before. It has been happening for several weeks now and I'm worried as to what it could be. I know I should probably go see a doctor but I'd like to get an idea of if this is normal or not before doing so.

Please help if possible!

I did a bit of research and here is what I came up with for different types of discharge

White: Thick, white discharge is common at the beginning and at the end of your cycle. Normal white discharge is not accompanied by itching. If itching is present, thick white discharge can indicate a yeast infection.

Clear and stretchy: This is fertile mucous and means you are ovulating.

Clear and watery: This occurs at different times of your cycle and can be particularly heavy after exercising.

Yellow or Green: Probably indicates an infection, especially if thick or clumpy like cottage cheese or has a foul odor.

Brown: May happen right after periods, and is just cleaning out your vagina. Old blood looks brown.

Spotting Blood/Brown Discharge: Occurs when you are ovulating. Sometimes early in pregnancy you may have spotting or a brownish discharge at the time your period would normally come. If you have spotting at the time of your normal period rather than your usual amount of flow, and you have had sex without using birth control, it is recommended that you take a pregnancy test

But the only way for us girls to really know what going on with our bodies is to visit a doctor

I figured I need to go to the doctor. I've lied to my doctor on the past visits when questioned about being sexually active. I'm afraid to admit it because I don't know whether or not they'll inform my parents (sounds silly but my parents are very strict and against sex before marriage).

It is illegal for them to tell your parents about it. You need to go get checked out.

Maybe I'll try getting a home pregnancy test first... then I'll go to the doctor.

Well, unprotected sex is dumb. 7 seconds to put on a condom, lol. he wont lose the boner.. Guys have precum, which comes out any time before he ejaculates, so even if he pulls out before the big orgasm, you still may be getting precum inside of you.
Since youre 18, you can go to the doctor your parents wont have to know about it. I'd recommend you do that, because hardly any of us are specialists on this site lol.