A few things -

1. I weigh well over 300lbs, have been in relationships since... uhhh forever and just married the man of my dreams.
2. The man of my dreams had chronic acne and has acne scars and is still fucking gorgeous, like model gorgeous.

You need to stop listening to the voice in your head that is being a dick to you and telling you there is no hope. This voice is wrong, it is a jerk, it is not seeing the whole picture. Your skin will heal if you leave it alone, your teeth can be fixed, your kindeys and arteries are probably not that bad at 20, you're going to be fine.

All of this stuff about the future - honestly, we don't know what will happen. You could win the lottery tomorrow, you could go viral and make a million dollars. You need to navigate yourself away from this catastrophic thinking and thinking you've ruined your life.

Yes, you have obstacles, but all of them can be over come with time and effort, and many of them are not the obstacles that you are making them out to be.

Don't give up, love your pets, love yourself, go to the gym, work hard at your good job. Build a life you love, things will come in time.

(Also maybe get a happy light or something, this time of year is really rough with the limited sunshine and it can make our brains be big jerks.)