ok, listen dude.
i was in the SAME shape you are in about 2 months ago. I hid it from my girl for about a year, year and a half and it got to a point to where i was like, this is fucking stupid, im a grown man and if a woman dont accept the fact that i want to do something that i really want to do, shes prolly not for me. So, i got my girl after a night out was dropping her off at her place and i told her earlier that i needed a "talk" so i pretty much just said that i use to smoke in highschool and i was completely ok with it, and that i was starting school again soon and i need it for concentration, i really do. ive been diagnosed with ADHD and adderall just isnt my thing. i understand if you get mad and i expect that, but respect that im telling you that i can let u know anything about it and its completely healthy.
i really dont remember the rest because it was pretty intense because she wa just a drinker and though everything else was a "drug" not knowing alcohol was a "drug".
so after a few days of awkwardness she finally got over it and is now a true pothead with me, in less that 2 months. im not saying this will work for you, just sayin it did for me, good luck brotha and remember u only have one life. they'll always be girls, and smoke.