where was I going wrong in this game?

I was playing this game 

https://www.chess.com/analysis/game/live/6097729589

Opponent was white started with e5. I black replied moving the queen side bishop pawn, to c5, which I understand to be the sicilian defense. So was  1 e5 c5

After that though, he stays way ahead of me according to the engine. Until he blunders his queen and resigns.

I didn't do any blunders.  I have been focussing on not blundering... by considering if he can attack me before I move.. considering if he can attack me after I move.   Trying not to leave hanging pieces.  (besides considering how I can attack him).  And I was fine re blunders, no blunders.

But the engine still put me quite a bit behind and i'm wondering why and where I was going wrong?

Thanks

2.e5 is a poor choice and was the cause of your discomfort. At the very least it's way too early to play this move. You are leaving a gaping hole on d5 and the main reason this is usually bad is because it's a beautiful square for a white knight to occupy. What happened to you is a secondary concern in that you cannot now blunt a Bc4 move effectively either (by playing e6) and this allows white to make some immediate dangerous threats. 2.Nc6, d6, g6 or e6 are all better and less committal moves than 2.e5.

Thanks.. So I have a gap on d5,   On that diagonal where my f7 oawn is.  But so does he on his equivalent - d4. Though he can attack my f7 pawn with his bishop. And I can't attack his f2 pawn with my bishop because my c5 pawn is blocking me.

So it seems like I am at some disadvantage in my 1..c5 opening, though it's a standard opening?

Also I wasn't seeing his knight jumping to d5 as something he'd do or a threat, because if he does, then if he gets any closer he's dead. So if he moves his knight to d5, then does one more attacking move from there, his knight is dead. By my queen or one of my pawns. 

Sicilian defence is an absolutely fine opening and indeed is the most popular choice - but there are dozens and dozens of ways which the game can progress with lots of subtleties. This is why it is popular, there is great variety. The weakness that you gave yourself on the d5 square is a serious long term issue - the point is not necessarily that white will play Nd5 and then jump again from there, it is that you will not be able to remove it from d5 and from there it will constantly restrict your position and threaten to jump dangerously. You are referring to immediate consequences, but it is the long term consequences which make 2.e5 a bad move. 

usually in the sicilian, black plays e6, preventing the knight from jumping in. once you play e5, you are no longer able to play e6, creating a hole in d5. 

beyond e5 pawn move which people have discussed is your pawn h5 move which might be instructional to you if you examine it. the computer rewarded white a full point of positional value you might ask: why? best there was probably castle queen side or more likely try to get your queen active again. If you look at how hard it is to get your queen involved in a plan I think that contributes to why the computer dislikes your position. nevertheless it was still better to find an idea for your queen. h5 gives your opponents Bishop free movement, makes your king side castle worse and your opponents king is not committed to either side yet and for you it doesn't help get your queen developed or make your king safer. my rule of thumb: (take with a grain of salt) when

Thanks. Regarding the  a2-g8 diagonal and path to an f7 attack. The channel seems to me to be just as open before e5 as after e5

The a2-g8 diagonal seems to be just as open before e5 as after e5, though a difference I see is that if I hadn't done e5, then I could have done e6 and blocked that channel.

So is e6 a must at some point in the sicilian defense?

You must be adaptable...e6 is sometimes necessary and good, sometimes not. I will say though that if white plays Bc4 it is almost always a good idea to play e6. The white bishop doesn't really belong on this square in most Sicilian scenarios as it can be chased away. By playing e6 you stop any threats against f7 and can then think about chasing it with a6+b5 or even d5 if possible.