I work 70 hours a week doing nothing but fast paced cardio, basically. I run, walk, lift objects 50-100lbs constantly and for at least a few hours of the day I have my hands over my head holding objects up.

What do you do? Work for Amazon?

The doc said I have an issue with my thyroid over accelerating my metabolism

Human metabolisms don't vary that much -- even in light of metabolic disorders* -- don't vary that much. In the end, our bodies all convert food to ATP at the same basic efficiency rate, and our cells all use the same amount of ATP to go about their business. So while I'm not arguing that your metabolic rate may be slightly altered, we're not talking big numbers here. We're talking, like, single digits at best.

I'm doing pretty good with money.

I just meant that there are a lot of people who get by with far lower food budgets. $450 a month? Man, I could eat like a king! Might want to head on over to /r/eatcheapandhealty, or /r/fitmeals and do some homework.

Anyway, look, it boils down to the fact that if you're not gaining weight, you're not eating enough calories. The more you eat, the faster you gain. It's that simple. Even if your estimation of your caloric intake is accurate (and I still think you're overestimating), the number still needs to be higher. But still, it's worth noting that 5 pounds of muscle mass in 2.5 months is an acceptable rate of gain. A half-pound per week? That's not abysmal. I mean, if it's all fat, then yeah, you need to re-evaluate. But if you've kept the same BF% -- or even dropped it -- then that 5 pounds is really nothing to sneeze at. Hell, if you kept that trend up, you'd gain 26 pounds in a year! That would be excellent!