Yeah I'll graduate right at year 3 after finishing an associates - which took me 1.5 years before. I just recently turned 30; there is no possible way I could have done it faster, because of work. If I was a full time student, no problem I could have got in done in 2ish. But taking hard science classes 2 at a time while working is tough, much less the few terms I added a third, or the time I was studying for MCAT. That, combined with the issue of finding classes that fit with your schedule sometimes you just can't get into the class you need, you'll end up taking longer than you expected.
And motivation? I know medicine is what I want to do, so you just need to remind yourself there is a light at the end of the tunnel, no matter how far away. This is a journey that is going to take what, upwards of 11 years by time your done with residency after you get in. Rushing to save a couple months here or there, or even a year, is totally, completely, unwise. In the scope of things, there is NO reason to not take extra time, be it for studying for MCAT, or taking an extra term or two to make sure you kill your classes.