I cant join servers and when I do I lag heaps

[Kami334]

I am having issues playing B-Team. Whenever I try to join a server, it doesn't let me, coming up with Bad Login, even when I restart. If I do join a server, I lag heaps, even worse then my friends, who live real close to me, and have roughly the same internet speed as me. Its not my computer, as it has been made to run games like this, and its not the server, because I have worse lag then anyone. Its not happening on other modpacks.

Please Help Soon!!!!

[BOMBMAN95]

Yeah this is happening to me accept it hasn't actually let me in, just says bad login.