How can I improve?

I need some advice on bass playing. Just a little background. I played about 5 years in the late 70's and early 80's. I learned playing bluegrass music. I was one of these who tried to play a lot of different instruments(bass,banjo,guitar,mandolin) but bass is by far the best. I also played in a Rock band in high school. I went many years not playing anything and I have taken the bass back up and have been playing a lot. I play every Sunday for my Church. I also play for my Quartet on songs that we use live music with instead of sound tracks. We practice about 40 minutes before the service on Sunday mourning, then we play about 6 songs total during the service. Then that evening we play about another 40 minutes for Choir practice and then about another 6 songs on the evening service. I know the fretboard very well so usually all I have to have is a key. I can play blues, country, gospel, bluegrass. I am very creative in playing at least on some songs. My problem is when I try other music like Jazz and some songs that I dont know at church. I really have to hear the song a few times untill I get it especially on some of the slower stuff. My question which I belive I know the answer. What should I do get get better. Most of the bass instructors in my area teachs by tab. I cannot read music. I dont even know any scales. Even though most songs are pretty basic I put a lot of runs and fill ins. Would I be better off just taking music lessons. Maybe I have just learned the wrong way. Any suggestions or advice.

Thanks
Steve