Getting my Arm strength back up

Okay well I haven’t pitched since about May of last year, and want to get my arm back to normal. I have thrown for the past 2 days [just started pitching again] and have already gotten a sore shoulder. [Right next to the armpit not to my chest side the other side. So I want to know what else can I do besides throwing that will help me conditon my arm? I want it to be ready by Middle to late March.
Thanks in advance for the help

You say you haven’t pitched since last may but have you thrown at all during that time or have you not done any throwing at all?

I haven’t thrown much I took all of the summer off went to the dominican republic. I played a couple pickup games in sept and oct but thats about it. I feel that my arm has gotten weak and after 3 days at pitching about 60% my arm is sore. I have a feel for my curve and my change shows some movement, but I have lost a lot on my fastball. Probably 20 mph. I know real emberising. I was throwing probably 60 to 55 last year and now im at im guessing its closer to 35. I know that the rest of my body has gotten stronger and I hae grownna bit so I should be able to pass 60.
Im 5"7 maybe 5"8 14 and 131

In the beginning of the season, sore arms are often due to too much too soon. If you haven’t been throwing at all, then you need to start off slow and work your way up. I would not recommend starting up again by pitching right away. Maybe start off doing a week of short/medium toss, then a week or two doing long toss, and only then start pitching. And once you start pitching, you should start off with smaller numbers of pitches and work up as you go.