I totally agree with Meyers Briggs. ISFP here I took it when I was 18 and more recently and I am still the same 30 years later.

One thing that I did for self discovery when i was feeling the way that you are now OP is that I would just sit down with paper and start brainstorming what I like and what I don't like and write everything down. Its a real eye opener.

I first start with off the top of my head likes and dislikes and then I will start formulating questions for myself

I have a feeling that you were rarely asked what you like when you were younger (I almost never was, and when I expressed a preference I was emotionally penalized for it, so I lost track of my likes and dislikes for awhile). You get to figure it out now, which can be a lot of fun for you.

Try with some small things like maybe ice cream (Love :d). Go to 31 flavors and pick out what you like and don't like. My favorite is the Watermelon Sherbet with the black candy watermelon seeds in it. Please complete this assignment and report back. If you don't have a 31 flavors then please find a reasonable facsimile. *hugs*

Hang in there sweetie. 19 is still really young.