Sexual Relationships 
Sexual Health 
When he seems to have gone off sex. When nothing seems to get him in the mood. When he's the one with "a headache" or he's "too tired" and you start to worry if it's you or he's seeing someone else, chances are you're wrong. Before you start convincing yourself that it's your fault, or he's gone off you consider this alternative. He could be having problems with his erection. Many men find this embarrassing or feel ashamed and would rather make excuses like being tired than admit what's really wrong.
Obviously the first thing he needs to do is visit his GP (easier said than done) and get checked out to rule out any underlying medical conditions. The most likely causes are stress, depression, smoking, being overweight and tiredness/fatigue. Talking to someone is also hard but can be very effective.
Erection problems usually aren't permanent unless there is something medically wrong. Changes to lifestyle such as exercising or reducing stress can fix things. The hardest part is loosing the fear. It's a vicious cycle. After a trying day he looses it halfway through. He tries to convince himself it's a one off, and it probably would be, but the next time he's getting busy he starts to worry about loosing it so he does. The more it happens the more likely it is to happen again. If he can't get control of the fear it could get so bad he can't get an erection in the first place for fear of loosing it.
So what can you, his girlfriend, do to help?
• Encourage him to open up to you. Drop hints that you're aware his having problems and it doesn't worry you. (Many men fear loosing it not because they can't get off, but because they think they're letting down their woman).
• Suggest doing other things. Take the focus away from sex and focus on foreplay type stimulation. Maybe make it a challenge - "I bet you can't get me off only using your tongue"
• Be supportive. If he says he's not in the mood then don't push him. Don't get offended but let him know you'll be ready if he changes his mind
Don't make the mistake of thinking he's not horny. All the urges are there, and he's probably as horny and frustrated as you, it's just that one part of him isn't being a team player. It's easy to think he doesn't want sex and that you're the only one not getting your itch scratched, but you'll find he wants it just as badly as you.
You may think it'll help to put on some new sexy underwear or try other ways to turn him on and get him in the mood but that's not as helpful as it seems. All you're doing is putting more pressure on him, and pressure is the last thing he needs. Try taking it slower; move back to kissing and cuddling, work together to find other ways to share intimacy without needing full sex. If you're playing around and things happen then enjoy it and don't make a fuss if he loses it. If it doesn't go any further that's fine too. Be there to be supportive but don't make it into a big deal and don't add pressure.
With time and understanding you'll be able to help him through this. It won't be permanent as long as you help him move past the fear.
I'm not an expert but you should find this at least gives you somewhere to start. Good luck and continue to be there for each other.
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