So I seem like I'm in a rut, always tired no energy I wanna exercise but it's only for a short time…

So I seem like I'm in a rut, always tired no energy I wanna exercise but it's only for a short time frame like I'll get ready to go to the gym n be pumped n then when I actually go to get in my car I'm like blah my mood changes n then I cry and I do yoga at home but I just can't shake this thing I got goin on... my friend says I'm lacking vitamins for my hormones not to act right I'm on my period but this has been lasting a few months I'll be 30 in march so my mom said I could be doin a mid life crisis I just don't know my moods are all over the place!!! I just need help but I wanna see if I can help my self b4 I see a doc. Any ideas?