Mash temps are paramount to fermentability and body. If your temps fell low during your mash,say down to 150° or less, then you would definitely have a lighter bodied beer.
As far as head retention, there are many factors that can affect it. The most common would be a dirty glass, or not a "beer" clean glass. Others factors can include poor hot and cold breaks and lack of carbonation.
So keep your temps within range, throw a blanket over your MLT, or find a way to insulate it. Make sure you have a good hot break and chill quickly to get a good cold break. Make sure your carbonation levels are on par approx 5oz/5 gallons, or 1 oz/gallon, that should get you to abut 2.5 volumes. Most importantly make sure your glass is wiped clean. FWIW, I never glean any of my drinking glassware in the dishwasher, and I hand dry and polish my pint glasses right after washing.