Did you resign all your players that you picked up in free agency the year prior on one year contracts the day after the superbowl? You only have one opportunity to resign those one year deal free agents and that is the week you advance beyond the superbowl. If you don't sign them then, they enter free agency. That could be where you see the money coming from.
Also, it's possible that the salaries don't roll over to the next season's dues until you advance to the preseason. If you reworked any deals during the season, you won't know quite what impact that will have until the preseason, and any cap penalties you have incurred won't clear until the preseason starts. There are a couple of things you can do to clear cap space. I have a number of guys signed to enormous contracts and I'm still keeping a $10.2 million cap overhead.
Also, it's best to avoid ever giving players guaranteed money (bonuses) if you are able. It's understandable to have some guys with guaranteed money. Rookies always get some amount of their contracts guaranteed and grabbing a bunch of high draft picks (1st rounders namely) will throw you into salary cap hell really quickly. Also I'm sure guys who were already on the team when you started the CCM have some guaranteed cash on their contracts. When you can resign them, just rework that to ensure no guaranteed cash and try to sign them to max-year deals. This minimizes the initial contract hit and increases the amount dramatically in the last 1-2 years, so you can keep a guy for most of the life of the contract with a lesser contract hit and then consider trading or releasing at a much later time. Also, spreading these deals across your playmakers as far as what years those contracts are going to be re-negotiated (you don't want all your big money guys signed so that one year you're paying a number of guys big $$$) goes a long way to your flexibility in cap space. If you have 6 guys for instance, you might want to sign 2 to 4 year deals, 2 to 5 year deals, and 2 to 6 year deals or something of that nature.
There is a place where you can check your salaries as well, it's in the same menu that schemes and team needs are in, the name slips my mind at the moment. I really need to take less time doing this
and more time doing this
. Remember kids, stay in school!