Write down the things you want to talk to your doctor about in point form. Keep it very simple. That way if you just can't seem to bring up mental health, you can just say "I have these concerns also" and hand him the 'list' (for want of a better word).
As for the worry that you'll come off as a nutter, try not to let that get to you. Seeking help with mental health is becoming more and more acceptable and the alternative is silently stewing away and letting things get worse. You deserve to be happy. You deserve to be helped to achieve this if this is what you need.
Write your list, check it twice and you won't fumble over your words.
Good luck.
'People are never perfect but love can be. People waste time looking for the perfect lover rather than creating the perfect love' - Princess Leigh-Cheri from Still Life With Woodpecker.