happiest-never despair. Ive had some tragedy in my life-cant get too specific at the risk of being recognized-but I also at one point thought that same way. I didnt have a mental illness,so to speak,but after what I went thru I did become depressed. I saw an amazing therapist, for around 5 years and she really helped me. If I can get married and raise a family, you sure can. The important thing is to have a good therapist/Dr. that you can connect with. If you dont click with one,go out and find one that you do click with. It is so important to be on the same page with your therapist. And find a support system, someone that you can vent to and cry to every so often,when you are in between sessions.
I would also put off dating until YOU feel ready to get started. It doesnt matter that now you are at the age to start. You need to feel it from within. Dont get forced into meeting someone if you are not ready. Its ok. We all have our own personal timetables. Just because your friends and your sisters etc. started dating at this age,doesnt mean that you do do too. I learned in my life that you need to do what is good for you when its good for you. We dont live for others.
Good luck!