As a Route Sales Manager for Interstate Batteries, I can tell you that 98% of peoples problems with Optima batteries is charging. I can guarantee you are not getting it fully charged from whenever it was discharged. See if there is an Interstate Battery "Distributor" in your area, they can perform a charge and check for you, wether yours is an IBS p/n or not.
If there is no Distributor near you, try taking a charged batt and run jumper cables to your yellow top, a good couple of hours. This brings the surface voltage of the battery up to where a charger will recognize that it is connected to a battery. Most all battery chargers that are on the market are proccesor controlled, an Optima's design allows it to provide peak performance below 8 volts, where most chargers do not go that low. Lead acid battery charge acceptance is between 5-7 amps per hour, any more than that you are just creating heat and shortening the lifespan of the batt. Optima says you can charge at whatever rate you want, as long as the battery doesn't exceed 125 degrees.
I hope this helps, I am a big fan of Optima Batts, I guess that shows. I know the bad rap they get, because of this exact problem. I have Optimas in everything, even my wife's bone stock Navigator, and a red top that is 9 years old in my Talon. You just spent a couple hundred bucks on a yellow top, I dont want you getting a bad taste for no reason. Also, a yellow top was the wrong application for you unless you have some massive stereo or offroad lights or something. Red top is the right thing for pretty much all of us, unless you use a blue top because of the handy dandy marine terminals.
