Sorry if this comes across as dumb or obvious to anyone but im trying to teach myself and its not too easy, anyways..

I just learned how to do alternate picking its really fun to play some metal I always just played punk rock before. I want to make up my own songs with and it feels natural to do a lot of downstroking at times.

Do you mix both if your playing a metal style at any times? Am I fighting against myself not going with what I know?

I think im just way over thinking this and im having a hard time explaining myself. At the end of the day weed helps me play guitar.
Your up-strokes should be, optimally, with as much power and tone as your downstrokes. That being said, I find certain passages to simply sound 'more metal' with downstrokes (Master of Puppets being an obvious example), so if you're more comfortable with downstrokes and know when you need to alt pick, you'll be fine.
modes are a social construct
Of course you can use and mix both. Personally I mostly do my rhythm parts with all downstrokes, especially when palm muting, and only use alternate for parts that are too fast to be downpicked. And pretty similarly, all the lead work that I do tends to be alternate or economy picked.
Don't know if weed helps with playing though. Never tried myself.
Maybe these articles will help you:

- http://www.guitarlearningtips.org/guitar-technique/what-is-alternate-picking/

- http://www.guitarlearningtips.org/guitar-technique/alternate-picking-exercises/

Things to keep in mind:

- alternate takes time

- it is better to practice a single pattern and become faster and faster rather then practice 1000 patterns.

- practice until your picking hand muscles develops

- practice with a metronome.

Good look

PS: Those exercises are very good although it may seem simple. Michael angelo batio, Rustey Cooley recommended them