Construcive critism please!

I feel like I've been a really bad girl friend recently. My boyfriend just started his last semester of university and he has class 4 times a week and works once a week so he's a lot busier than he used to be. Which was twice a week and one a week for work too. Please keep in mind that I love this man endlessly and all I want is for him to be happy and having success. I'm a really moody person especially when it comes to my period, and mines coming soon so I'm all over the place with emotions. I always feel so sad and lonely when he's busy with school and work. I've been feeling like he's bored of me or doesn't want to talk so much lately and I know it's because he's busy with his life but it just sucks. I've talked to him about it and I said I would be more understanding of him but I feel very overwhelmed with emotions right now and I'm afraid of bringing it up because I don't want to annoy him with yet another argument. I love him so much and I don't want to mess things up. Someone please knock some sense into me?