What's your stream resolution and FPS? For 1080p (1920x1080) and 30 FPS your bitrate shouldnt be lower than 3000 kbps, it supposed to be somewhere between 3000 and 6000, depends on your hardware capability.
If your system cant handle it, lower the resolution first. For 720p (1280x720) your bitrate should be somewhere between 1600 and 4000 kbps.
Also you always can lower the game's settings. Try to set everything on minimum, except the screen resolution, and do some tests. Usually the game have a priority, so if your PC cant handle the game and video coding at the same time, the first one could be running smooth, but your fps in video could drop to unviewable levels.
Could be just an internet issue also
Do some internet stability tests. And also if you are using Xsplit, try to do some tests in OBS.