Problem with receiving emails…….

I'm having problems receiving emails. for about 3 months I've had many emails that I've been expecting not hit my account. Sometimes they turn up 2 months late after the original sending or not at all! I've checked my Junk, my settings about blocking, about forwarding, filters, rules etc etc and everything in settings looks fine. People ring me up fuming that I haven't replied to 5 emails they've sent that I haven't received. These are the ones that I know about.... Especially as I work freelance, my email address is my work. I've changed my password to see if that helps too..... It's strange because there seems to be no consistency to it, as it's indiscriminately effecting my contacts, new senders and god knows what else. Please help!!!