I would think you're just not eating enough and your BMR is catching up with you (and by that I mean that over time your body has adjusted so that it burns a lot less calories now because you barely feed yourself).
I would suggest increasing your caloric intake, but if possible do so by eating healthy meals (i.e. steer clear of frozen foods or microwavable foods)
Mixed nuts (from Costo, supermarket, wherever) are a GREAT way to get in a lot of healthy calories and healthy fats. I believe the ones I purchase are 200 cals per serving, which is 1/4 of a cup. I usually eat about a cup's worth a day. They'll keep you pretty full as a snack too!
not sure if you mentioned it but I can't see it anywhere - are you male/female? I am assuming male just because of your height but I could be wrong.
Anyway if you weigh 225 you should definitely be eating a lot more calories than even 1,600. You can google a BMR calculator, which will give you the amount of calories you burn just by doing things like keeping your heart and lungs running. This is the absolute bare minimum amt. of calories your body needs in a given day for you to be alive. You should shoot for over that because any activity outside of just lying in bed will burn extra calories. As long as you eat somewhere above your BMR but below the total number of calories you burn in a day you will lose weight.