Should I marry my girlfriend?

she was my first serious relationship and early in our relationship i got her pregnant and we movee in together and i told her i would marry her and at the time i wanted to. she had a mischarage and we never got married. now when i finish school i will be moving away and im in a situation where i have to marry her or she stay were we live now. i love her and there is nothing wrong with her we get along great weve been tigether 2 years but the problem is marrying her doesnt feel right.if we did get married im sure we could have a good marriage but i cant pinpoint the reason but shes simply not the one even though shes a great good girl i just have a feeling deep down inside. anothr oroblem is she needs me finacially and if i told her i dont eant to get married she really has no familyeither so i feel like iamgoing to screw her over. shes alo several years older and stikk has in her head that im going to be her future husband