I believe you can freeze any that you wont use in the first 30 days by drawing it into syringes and placing them in your freezer. Just take them out and put them in the fridge a day or two before you need them. I've heard arguments that freezing could affect the potency but I believe that was debunked. Even if the potency is slightly affected, it should be less than the natural decrease of potency that it has when sitting in your fridge longer than 30-60 days.
As for the cost of it, my compounding pharmacy sells 5,000 iu for $80. I didn't think that was a very good price so I decided to get it from CVS Caremark Specialty Pharmacy. My price with them is $79 for 10,000 iu. However, I think my insurance gets me that price. Im on a High deductible plan but some medications are covered at 100% and others are not. For example my AI is free. I say all that just so you know CVS does have it, you just have to go through the specialty branch. Im not sure what insurance you have but my coverage was denied the first time my doctor wrote me a script. I had to file an appeal. Upon a second look, my condition (secondary hypogonadism) that my Doc put on the script was an acceptable reason to have HCG according to them (United Healthcare).
Regarding the necessity of HCG while you are on TRT, people will argue strongly both ways but in the end it's up to you to decide if it works for you. You said you had shrinkage and pain. Those are both symptoms that HCG is known for helping in scenarios like yours.