I think that I figured out how I was so far off. I measured my water and then mashed and sparged and assumed ( ass out of me for sure ) I had 7.5 gallons of wort in the boil. I never mesured the actual ammount of wort befor boiling. My missing volume must have been soaked into the grist.
Yes, that would do it!
I'd put a volume marking on a big stick or spoon and use that to gauge your volume.
When you mash, you can expect to lose about 1 gallon of water to 10 pounds of grain (actually, usually about 1.25 gallons). So, in a 15 pound grainbill, you'd normally "lose" 1.8-2 gallons of that original strike water. Then, you sparge up to your boil volume.
So, in this example, say you were using 15 pounds of grain and wanted 7 gallons of wort for your boil volume (typical amount to start with for me).
Using 1.5 quarts of water per pound of grain, you'd use 22.5 quarts of water in the mash. Call it 22 quarts, or 5.5 gallons.
You'd mash in with 5.5 gallons, but only get out about 3.75 gallons (or so). That means you'd want to use 3.25 gallons of sparge water to get to your 7 gallon boil volume.
So, you're going to need 8.75 gallons of water to make that 5 gallon batch. This is a guestimate/average for me, and your system may differ depending on the deadspaces and things in your system, but it's a good place to start.
It's important to measure your volumes, especially at first, because it helps you determine your efficiency (important for using recipes and adjusting them) as well as help you troubleshoot any issues you have. You'll also want to take a preboil SG (cool it to under 90 degrees first, and then convert with a table) and a post boil SG to make sure you're on track. Volumes are crucial for these readings.