I can't log into my account

I can't log into my account. I changed my password several times, but it won't work. There will always be a red message bubble saying something like: "Password or e-mail invalid". I got the e-mail right. So it must be a problem with the password. ( It might be helpfull to say that I play with a Mojang account AND I got the password right. ) Any who, thank you for your service.