Are you getting any specific disconnect message? If not, navigate to your latest log (or the log in which you experienced the connection issues), and upload the log to a third-party such as Pastebin and/or attach as a file here.
Hopefully with this we can see if there's any reason as to why you're experiencing issues.
Note: some log files depending on your version of the game can include sensitive information such as your Minecraft session id, double check your log file before uploading or attaching anywhere.