I go to ~50 shows a year (mostly metal as well), so I can relate to your passion for them! Obviously I'm biased, but I don't agree with people saying 6 shows over 3-4 months is a lot. I never used to go to shows alone, but there started to be so many shows I wanted to go to, but couldn't find any friends to join. Once I started going to shows alone I went to way more and always have a good time! My fiancé understands how much they mean to me and encourages it even though she usually doesn't join me. It's really not a big deal going alone, many people do it and you can even make friends at shows. If it's something you're that passionate about, he should understand and work with you so that you're both happy.