1999 Toyota Tacoma Battery Problem, but is it REALLY my bat

I am a bit of a newb when it comes to car repair, so please bear with me. A month or so ago, my truck wouldn't start. It wasn't turning over, and I didn't hear the starter make any attempt to, well, start. My accesspries were powered just fine. After a couple of attempts, my truck started up and it seemed like everything was okay. A few days later this happened again. Soon this was happening everyday.

I checked the voltage on my batter, and it was a little under what I was expecting, but not by much (I don't have the numbers on me, but I can get them). I made sure the water in the batter was full and that my batter leads & cables were cleaned off. I even used anti-corrosion spray afterwards. After I did all that, the truck seemed to start all the time. But the past two or three days this has been happening all over again. This morning it wouldn't start at all. I finally decided to see what would happen if I push-started it, and it started up just fine.

I know that the obvious thing to see in all of this is that I need a new battery, but somehow I'm not 100% sold on it. My accessories work fine, and sometimes I just need to try enough times to get my truck to start. Could there be something wrong with my cables that would cause my battery to power my lights and radio but not my starter?

Thank you