Cheating lying pregnant girlfriend, am I making the right choice?

So starting me and the girl got into the relationship at a young age. I was 17 and she was 15. I was a senior she was a sophomore, first girl I have ever dated that was younger then me. First off the bat things were shady but i thought it was just haters. Little stuff like she took a sweat outfit from me which was fine, and wore it to school the next day. I didn't ask her to, she just did it. Then a lesbian girl who liked her at our school gave her **** about it and my new girlfriend claimed i made her wear it. When word got back I figured it was just haters the girl that wasmaking the claim was always the center of drama. Then the rumors got worse to a threesome she had with another girl and a guy, once again i figured haters. the girl making the accusation tried getting with me a few days before and i turned her down of course. She then dropped out of high school a couple years later because she failed every class and went to an alternative school, i started college at that point at a local community college (In colorado you have to be 24 or older to sign your own student loan paper work, and i wasn't getting help withmy parents so it was all i could afford until i set a solid GPA which i did do). People kept telling me somethings wrong with her she is always around another guy all the time at her alternative school, I figured an alternative school a bunch of punks haters that got exspelled for start drama, some werent bad but a lot of them were punks. People then told me she was cheating again and it was always the same people, so haters. Come to find out the guys she was hanging out with at school was true, she did go to his house, she did cheat on me a couple times that i found out about, i couldntput soe of the older stuff together. When i found out she cheated she simply replied you shouldn't have been snooping. This girl got pregnant and claimed it was mine a couple months after the break up. After she caught a cold which developed into pneumoniania i was there at the hospital every night with her through every surgery, work at my bank in the day as a teller, and staying with her in the night and morning. After she got out of the hospital she claimed she was at work again at Carl's JR. Funny thing is my mom would go there to eat and see how she was doing, but my girlfriend wasn't there a lot of the time when she told me she was. She spread rumors i was out drinking and partying. (When i found out she was pregnant i got an ulcer, and shortly after had an anxiety attack which almost put me into cardiac arrest. I had to take pills to keep myblood preasure good and keep from stressing so much. I stopped taking the pills had a second attack, took the pills again and then startedworking out regularly again like i did in high school only being 19 at this point). I can't drink, i cant keep a single shot of anything down and she knows that, i can eat a lot opf things now but still some small restriction. People showed up to my moms work and asked her about it, at her work. I can't go to my local grocery store without people asking all kinds of questions of things they heard from her. Her lying is horrible. One day she said she was at work and went straight home. Well my mom said she saw her in Wal Mart with her friend. Not a big deal. I asked her did you go any where else and she promised "No". I told her my mom saw her there. She then said "oh i forgot". I asked her "did you go with anyone?" she claimed no again, I asked her can you promise me. She still claimed she went alone and got mad that i questioned her. I told her my mom saw her with her friend so i already know,. Every time she cheated i showed her the proof and she still denies it even to this day pictures, notes she left at my house that "fell" she claims out of her back pack and email. Her messages that she typed. Is it right for me to ask for paternityaty test, and not give her any more money. Just a week ago she was threatening to not give the child my last name and give me no parental rights, I figured my best chance of taking care of this kid, now that i am over the ulcer and not sufferinging of the anxieaty anymore is that i should do the Air Force to get my college done since i am to young to sign my own student loan paper work in this state,and i can't afford it any more with the child if the test shows he is mine. Now she wants the kid to have my name and wants me to sign the birth certificate. After years of my family telling me to stay away from this girl i finally had the last straw when she publicly announced on facebook what a bad father i am after i already talked to her about how embarrassinging it is to me and my family and how she spreads rumors. I now do see clearer and want a paternityaty test before giving her any more cash or locking my self in .I have read a lot about people that have lying issues and i believe she may be one as well and need to get awa