Insecurites

I will go on the record and say that I'm not as smart as I once thought that I was. Maybe I went into the wrong profession. Maybe I'm not meant to be a CPA. I study and study and study and I just don't care. I don't comprehend what it is that I'm reading or why they treat it the way that they do. I used to think I was pretty damn smart...then I entered my senior year and bit off more than I could chew and the disappointments just kept coming from there. I had a pretty crappy GPA (something I never had to worry about before college). I now have loans to repay and I don't make a big enough salary to pay for and live comfortably. I have a boyfriend that won't commit while everyone and their mother I know is either getting married or starting a family. I will be 28 soon and have none of that coming my way. People tell me that I can achieve bigger things but I always hear my mother in the back of my head telling me that I won't amount to anything. How can you get around that? I have never had words of encouragement from my family and when my co-workers do give me encouragement I just flat out don't believe them.