How to get back on track /?

okay so long story short I use to starve myself , binge and purge before and lost weight , the last month has been really stressful for me and I started binging and purging again , now im done school and have a little more time on my hands , im 136 - 138 - 5'6 , flabby , I wanna get back to healthy eating without over eating , i want to add muscle because im flabbly too , i have a gym membership and everything , where do I start ? what should I start eating ? how many calories ? I want that glow back in my face and dont want my neck bones sticking out like crazy , thanks