Good Morning,

I've not had a lump in my armpit before but having found 2 lumps on seperate occasions in my breast I have been referred to the breast clinic twice before and understand the anxiety this brings with it. In my experience it's a standard to refer any new lumps to the breast clinic in order to rule out the worst case, and they aim to get you seen within two weeks to minimise the amount of time spent worrying about it. In my case the first one was a cyst which required no further treatment as it was small and not causing me any problems, this has now pretty much disappeared which I have read they can come and go. The second time was just lumpy breast tissue that I was feeling. As you've said your lump seems to have reduced in size a little this is reasurring and probably will be just one of those things that comes with hormonal body changes or stress like you say. Although its a worrying time, the breast clinic really is the best place to go and have things looked at by the specialists and hopefully put your mind at rest by finding out what it is. 

I find the lead up to the appointment the hardest time and can only recommend you try and distract yourself until that time as hard as that can be, its best to not get lost in wondering what it might be and wait until you know for certain. 

Hope this helps and that you don't have to wait too long for your appointment :)