HELP PLZZ

We need more details please.

 ok this is what happened i was building my house i broke two blocks on my house replacing then the blocks didnt drop so i disconnected and tried logging back but it didnt work so i waitd a while and relised it said im online playing the server but i wasnt so i think a hacker using my username on my account and thats why i cant get in the server :(

The server probaly crashed and it is saying you are in it but you aren't.

 oh im not hacked i loggod on now servers just lagging

The server was crashed, the player list showing players like they're still online is just a bug from a crash.