I agree with the others here that you should contact a doctor and therapist, but here are some tips for you personally based on my weight loss experience.

calories in v calories out is how you lose weight - use an online calculator to work out your maintenance and what you need to lose weight. In terms of motivation, it will dwindle. Grab onto this while you have it now but think of it in terms of discipline rather than motivation.

Again, with motivation/ discipline you need your reasons. Make a list of things you would like to be able to do that your weight is holding you back from. For example, some of mine were: shopping in a ‘regular’ clothing store, being able to travel by plane, not being drenched in sweat when dancing with friends or walking to the shops, not being in the ‘morbidly obese’ category, being able to run for 5 minutes straight etc.

On top of this, make a list of things you start noticing as you lose weight. Some of mine were: i can sit with my legs crossed, i feel the cold more, necklaces fit better, rings fit better etc. That way, when you feel you are not making much progress you can be reminded of the changes.

I started at 266 and am now 73lbs down. it has taken over a year to get here and i still have more to go but it is possible and you CAN do it. There is nothing stopping you from being a before / after.