I’m in a complicated situation

I’ve been dating my gf for almost 7 months now and I’m starting to feel like I should break up with her. The main thing is that I’m enlisting and leaving for boot camp in just under 4 weeks and I feel like we won’t last in a long distance relationship anyway but there are some little things too like how I’m avoiding drugs like the plague. I used to smoke pot but I’ve stopped for obvious reasons and I don’t even wanna be around it for fear I’ll fail a drug test. She literally always tries smoking around me even when I tell her not to. She’ll start doing it while we’re in the car or we’ll be outside and she has the need to be right next to me while she does it. It usually results in me yelling at her because I’ve told her dozens of times. Another thing is that she’s been on spring break and has spent the whole week with me and she’s just been annoying the hell out of me and making me angry. Like we probably fight about something every day. It’s to the point that I’m ready for her to just go back to school. She also seems to have no common sense and literally seems like a brainless twat sometimes because she seems to just be into pot and stupid social media crap. I can’t have any type of intelligent conversation with her without always feeling like she’s lost interest before it’s even started. Last but not least she kinda seems like a slacker at times. She was supposed to find a job this semester and she applied to a couple of places and then never reached out about her app or anything. She puts more effort into pot then she does anything else which is aggravating as hell too. The main reason this irritates me is that I don’t want to end up marrying this girl and be paying off her student loans because she slacked off and can’t find a job with her degree because of a bad gpa and extreme lack of involvement on campus. I don’t know there’s just some things I’ve got concerns about future wise and things that irritate me now and I’m not sure what to do. I’ve never been the one to dump someone and really don’t wanna deal with all the crying and stuff and I like this girl I do but within the last month or 2 I’ve went from loving her to just not feeling that anymore and I don’t know how I can get it back.