From wikipedia: Pregabalin (Lyrica) binds to the 2 (alpha2delta) subunit of the voltage-dependent calcium channel in the central nervous system. This reduces calcium influx into the nerve terminals. Pregabalin also decreases the release of neurotransmitters such as glutamate, noradrenaline, and substance P (Australian Medicines Handbook). Pregabalin increases neuronal GABA levels by producing a dose-dependent increase in glutamic acid decarboxylase activity.[1] Glutamic acid decarboxylase (GAD) is the enzyme that converts the excitatory neurotransmitter glutamate into the inhibitory GABA in a single step. For this reason, pregabalin greatly potentiates benzodiazepines, barbiturates & other depressants.

This is very similar to the damage that monosodium glutamate (MSG) and aspertame cause (neurotoxins). It is not surprising that you gained weight and can't seem to lose it since these types of neurotoxins tend to disrupt the endocrine system which controls appetite and weight gain. For more info read
Excitotoxins: The Taste That Kills by Russell L. Blaylock, M.D.

To help fix the problem, you could eat more healthy fats like whole milk (preferably raw but definitely not skim or low fat), butter, coconut oil, tallow. Fats help heal the brain and help you feel satiated. Also, avoid any vegetable oils and food additives especially free glutamic acid. Avoiding fructose can help as well especially in the form of corn syrup but maybe even fruit - high fructose corn syrup is so popular as a food additive because it causes insatiable hunger.. Eat raw honey instead of sugar or sugar substitutes. Fermented veggies can help stop sugar cravings and are full of beneficial bacteria to heal gut flora.

I know this works because it is what I am doing to heal myself after free glutamic acid toxicity. As you can see, I have done a lot of research on this.