Don't feel guilty or try and make excuses for why people haven't called you.
It's not you, it's THEM
Like Yasny says, they could be genuinely busy, and push it to one side while something more important comes along - I do it all the time, and I would hate it if any of my friends were to think something was wrong with them because that's not the case - and if anything I feel really guilty.
I'm also quite forgetful and have often read texts/emails then something else comes up and it totally goes out of my head.
I also have a busy schedule, so trying to fit things in is hard.
Try arranging something you will both enjoy.
I think for those with a drink problem it's going to be hard to put something before alcohol - and surely you are better than that??