Hello, It does sound like he has lost the love/inlove feeling he once had for you and yet you both are best of friends and very comfortable with each other it is not enough for him and he seems to crave something else sexually. Once you are apart he probably realises that it is not as easy to get that sexual feeling and closeness he desires with someone else. Then he seems to come back to you. I am sure he misses you when you are apart BUT you deserve someone who wants to be with you all the time and loves you for you. Toss him as the roller coaster he is on is going to cause you emotional issues in the future and how can you trust him when he has hurt you so much already… for nothing.