Thanks for writing... your situation sounds quite difficult at the moment. Okay, I will break this down into two parts...
(1) Your depression has returned, although I am certain you are well aware of that already. Depression, and particularly the deep kind that seems to afflict you, tends to be cyclic in nature. In other words, it will grip you, run its course, and then ease over time. Unfortunately, the period within which you are low can be extremely painful, and must be treated lest you become actively suicidal.
(2) The "not being able to walk" really caught my ear - there is another condition called "Conversion Disorder" whereby a patient will essentially lose the use of a part of the body (eye(s), hand(s), perhaps legs) for no physiological reason at all. This disorder is trauma/stress-based, and can appear immediately following an exceedingly difficult situation, such as the one you described. Again, therapy plus medication is going to be the best course for you, regardless of the actual diagnosis, although a professional must be involved to ensure that the medication is correct.
The good news: These are very treatable conditions which will abate with proper help (too, you have received help and succeeded in the past, which sets you up for a more optimistic prognosis currently). The bad news: your emotional constitution may predispose you toward suffering through these bouts of depression off and on for the rest of your life. I am not saying they WILL come on as often or as strong as they have previously, but you will perhaps always be prone toward going through dark periods.
Get the help you need and allow yourself to recover. The relationship you wrote about may or may not flourish into anything permanent (intimacy can be so fickle!), but regardless of its long-term outlook, please see to it that you also surround yourself with competent professionals and people who will offer the support that you require. I do wish you well! If you are satisfied with the response, please hit "Accept." That is the only way I can receive credit for my answer. Thanks-