Stalking on my devices

I have reason to believe that someone has gained access to my iphone(s)/ipad/macbook and is spying on me. It seems very likely that they have been able to read my emails. It has only just come to my attention but has potentially been going on for two years.

I recently upgraded my phone and can't find any evidence of spyware on there but I do recall my previous iphone would get really hot for no apparent reason – I assumed it was just past its best.

We've updated the privacy settings on the router so I think it now assigns new IP addresses on a regular basis. Is there anything else I should be doing? I'm concerned about spyware and other techniques for stalking.

Thanks in advance