Low gpa, high upward trend

My situation is a tad bit complicated. I started college at a private Christian university. I went there for 2 1/2 years mostly taking Bible courses that had nothing to do with my major. During those two years I was making terrible grades (C’s and F’s) and having a tough time focusing. I transferred after the 2 1/2 years to a public university where I found out that I had done poorly previously due to ADHD. Once I got treated I started making straight A’s and the occasional B. I have been in this public university for almost 2 1/2 years and have only one year to go. My gpa at this university is a 3.8 and my science gpa is around a 3.7. However, the bad grades from the private college is landing myself at a cumulative gpa of 2.5. Should I do a post bacc to try to raise the cumulative gpa?