You're little one is precious! Don't worry about being a bad mommy, we've all been there. They are so quick. Maggie is just 6 mos old and was jumping off the back of our sofa!!! I think it is about 40". She is all of 3 lbs today so she was much smaller when she was doing this.
Talk about scary.
I have tons of pillows around the sofa so they can catapult up and jump down from the sofa. A friend of mine lost their dog and gave me their supplies which included a set of steps. It is just the right height of the sofa and they took to it right away. The have the same steps at Walgreens for 10.00 and at CVS also. We've never had them on the bed though.
Could your little guy just have puppy weight on him? Maggie was a little round for her size but she has grown taller and thinned out over the past month and half. Sounds like your guy may just have a cobby shape to him. Maggie is now about 8 inches.