Hi @NatF - welcome to the blog - I hope you are going OK!
I've been on Arimidex for 12 months this week, after 6 months of Exemestane & 6 weeks of Letrozole (both of which resulted in massive joint pain.) My surgery was in Jan 2018, with Rads.
Along with the Arimidex, I am also taking some medicinal oils that I do believe is helping relieve most 'other' side effects, including lack of sleep! However, I HAVE had the odd 'foot/leg' pain now & then. Usually it only lasts a number of hours, but is quite debilitating when at it is at it's peak.
I think that most of the AIs affect our sleep one way or another - and I do believe I have put on just under 5kg since starting AIs (Arimidex in particular.) But I've also had my normal exercise regime changed with this lockdown thing, so can't wait for it all to pass, so we can get back to our regular activities!
If you consider changing meds, I fear that your side effects may get worse? Speak with your Onc about them. Sometimes it is better the devil you know - but well worth either having a break from Arimidex for 4 weeks every now & then ..... or try the others & take notes on any potential side effects
Take care xx