Hi , my SCM was awful post surgery. Causing jaw ache, muscle twitches etc, and I' m sure that it was also the cause for triggering occipital headaches. I don't want to panic or stress anyone but I must be honest in saying that mine was pretty full on for well over a year post first rib excision surgery. Sorry folks... But on a good note, I'm now over 2 yrs post and my neck has settled a lot better since. However I know my limitations and try not to push them. I stick to my guns with not carrying too heavy a shopping bag, even if it means making multiple trips to get it done... I will not allow myself to carry anything too heavy, say, no more than 5 lbs in each hand!
Also, I forgot to add, unfortunately my lifestyle has altered drastically! I no longer participate in jogging as this pulls too much on my shoulders/neck region... I miss it like mad and I have gained an additional 22lbs! But at least my pain levels have reduced.

Take little steps, stretch, exercise etc but be mindful and take care.