@Poster. . . here is my 2 cents:
This may be 'bad' news so I suggest you see a doctor. If it is not anything that is caused by some other health conditions like diabetes, blood related problems, some physical damage to the p*nis, then it's potentially not as bad. You may be suffering from 'performance anxiety'. I don't think there's any need to write details here as you could easily 'google' it.
However, I know there are some drugs that might greatly help and get you back 'blasting' at full speed!

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Cialis, Viagra and Levitra are all good treatment options but you would need a prescription to buy them, over here and most (all) of the western countries. I don't think they are 'cheap' especially when the cost is converted to Naira; availability and authenticity may be a different story in Nigeria. Honestly, I don't know about that but I am sure you could find out. Before long, you wouldn't 'manage' and you could do it with your wife

anytime of the day! Well, guess what? Your confidence will soon return and you might be flying without wings!!

I also know that there are some you could buy online but this might not be the 'original' ones but I know there are several pharmacies online. You can google to look for online pharmacies and if you could buy from any. However, do your research properly before parting with your money for this option.
The best option is to see a qualified medical doctor to be sure there are no underlying medical conditions and if he recommends any drugs, he might also be able to recommend where you can buy original and not fake ones. I know if you are in Nigeria, it wouldn't be too easy but you gotta try and fix the problem before it gets worse! Finally, reduce the masturbation and let your wife/girlfriend help you out. Relax! All the best, man!