Woodland & VL,
I know just how you feel. I'm having an "odd" knee pain, and it's scaring the wits out of me, and it is hard to know what's paranoia and what's rational concern; add to that the "I can't do this again" fear and it can be quite overwhelming.
But back to lymphoedema. There's all sorts of things to do to help--to start with check out the Lymphoedema Support Network: http://lymphoedema.org/
Things to remember: deep breathing helps. Keep your arm elevated as much as possible. Drinking water helps. Salt or alcohol can make it worse. So can extremes of hot and cold (including weather and bathing). The Haven has some lymphoedema excercises on their website that may help.
www.thehaven.org.uk/how-we-can-help-you/lymphoedema
There is a bcc factsheet on lymphoedema too. Once you start wearing the sleeve it WILL help--especially with the ache. Raise your arm over your head (or as high as is comfortable) and pump your fist five to ten times. Exercise helps, but not excessive excercise--gentle and slow is the rule, but exercise gets the lymph moving. Lots of women have said swimming helps (I don't have a pool to use).
There's an American website "Step up Step out" that I find helpful, but I'm a Yank, and many of the UK women seem to be uncomfortable with it.
Gently stroke your arm from the top (by shoulder) working your way down for about ten minutes. Divide your arm into about six 'sections" and stroke each section upwards in short strokes (like you are stroking a kitten--the lymphatic system is RIGHT under the skin so pushing hard is counter productive. A video that shows a good way of stroking is here
www.youtube.com/watch?v=pSD7j8mSVkM
She has you stroking more than just your arm, but I would wait for your lymph nurse to help you with that.
Insist that you see a trained Lymphoedema specialist.