LDR bf says I may not be "the one"

Sam
We've been dating for a year and a half & we've been in a LDR for about 3 months nowI asked him why he said this & he stated because he's looking for someone who is healthy and works out. Before we started dating I was always healthy, but I was constantly being dined by him and we didn't have a lot of time together so we both stopped working out. I gained about 15lbs He always said that he didn't care but all of a sudden he does & if I don't change soon then he will leave? I knew that I could not focus on college and work to support myself so I joined the military. I had a hard time with college at first, but I am now getting all As now that I have adjusted. Although I am following my plans, he constantly tells me to get a job and said that I was ambitious when he first met me but now I've gotten lazy. He also put down my new accomplishments by saying that they weren't **** bc he knows people taking more credit hours Then covering up by saying "I'm just saying that I know you can do better." (It was the summer semester which means less classes offered, but fast pace) I know that I have stopped working out as much as I used to & I am working on being healthier but I am put off my someone saying that if I'm not a certain way then they don't want me. I'm not looking for a pity party here, I would just like to know other perpectives on this matter. On one hand I can that he wants me to be healthier but on the other hand I don't see how he can say that he doesn't know if I'm the one randomly when he was just saying that he wanted to marry me and what not