slow downloads even with new XB7 Gateway

I had an XB gateway.. maybe XB3?  It was running really hot and getting louder.  Plus, my set up says I have Blast! Pro Internet with downloads as fast as 275 Mbps, I was getting about 37 Mbps. 

I called and after a painful conversation with a woman, she shipped me an XB7 Technicolor CGM4331COM.  I've got it set up and am still getting 32.7 downloads and 17.9 uploads.  My gateway goes into the wall, sharing a splitter with my DVR box, the way Comcast set it up.  I've had over 100 Mbps in the past, these really slow speeds are recent.  And paying over $200 a month is making me cranky when webpages take so long to load.

Any suggestions?  

I saw a message about making sure the firmware is up to date.  Where do I look to check on that and how do I update it, if that is needed?

Thank you,

Michelle