You'll be fine, the first week back is always the worst, I often feel quite lost and emotional during the first week. It's a combination of jetlag, back to the reality of work and of course missing your loved one, but it does get better.
I really have found that booking flights in advance works for me, it gives me a sense of knowing, rather than just wondering if and when I will go back. The other advantage is booking in advance usually ensures I get a reasonably priced ticket.
I can't use Skype anymore, it hurts too much, seeing and not being able to touch. We keep in touch via YM, FB and SMS throughout the day.
LDR's are hard work and take a lot of effort and commitment, but if you are sure you have found your soul mate, they are worth every ounce of effort you put into it. Ultimately, you won't be apart for ever, as sooner or later you will both make a decision to be together.
There are bound to be many more dark days ahead, and don't forget we all know what it's like, we've been there and still have them too. The beauty of this forum is that we are nearly all in the same boat and can help each other get over our bouts of anxiety, paranoia, depression...etc. We aren't like your mates in the 'real' world who simply don't understand what you are going through.
Try not to torture yourself too much, and remember the wonderful times you and your mahal spent together, whilst at the same time remembering that soon enough you will be in her arms again