telling my boyfriend about cramps/being on my period

we're both in high school, if that makes any difference. we've talked about periods before so it's not like it's a new topic and would be super weird... but I've been really tired due to my period and I've just felt like absolute crap. I want to tell him because I always feel better when someone else knows what's going on with me. I just don't know how or if I should.