Good comment, I have some to add

The reality is that almost all engineering students feel this way. In my opinion, it is mostly the fault of an outdated educational system that teaches engineering in ways that are not beneficial to most students. What worked for me was to get involved. We had small research projects at my school that were 1 credit that you could work on and get some hands on experience instead of crunching numbers through the night. Those were really helpful to me because they kept me involved and put me in contact with other people that were interested in the same stuff.

As some others have said, engineering school is more of a test than a representation of what you can expect on the job. However, it's also good to keep in mind that your options are very open after graduation. I've found that engineering degrees are highly respected because it shows you are capable of getting through what some would call hell (engineering school). I know people that have gotten jobs in business management or completely unrelated creative stuff.

As far as the weed goes, it's simple, know the line between work and play. If you feel like it is becoming a crutch, stop or at least cut back significantly. Anything that alters your state of mind has the potential to become an unhealthy crutch. I'm in grad school now and work my ass off through most every night but sometimes once I've reached a good stopping point, I'll sit back and vape (Pax is also a good idea) and enjoy a reward for hard work.

Lastly, if you feel that you are more than just stressed and unhappy from your major, please go to counseling services at your school (free and confidential). Depression is no joke and you owe it to yourself and everyone that cares about you to address it if you are feeling depressed.