Let me begin by saying that I do enjoy reading your comic. It is one of the 2 or 3 that actually has some interesting characters. I wasn't impressed when I started reading it, but it's gotten better as it goes along and I've been reading for over 5 years now.
The only problem I've been having is that you seem to be writing a novel, not a comic strip. Novels can be more detailed and can afford to spend time on a single scene because it does not have to be drawn and can be typed and/or read all at once. You can afford to put in every conversation and what every character is eating. You can't do that on a comic. If you try, you end up spending 6 months on a single scene. The future characters are going home from a dinner party that they left for last May.
On that basis, though I did like the jokes of Tessa ordering Fish & Chips, I didn't really need the information. It makes the story drag for the reader, and if this story is dragging for us, It's probably been doing the same for you. Leaving all else aside, if you continue at the pace you are going, it will be another 15 years before we get to the end.
I don't criticize often. I like this comic. I like the story, I like the art, I like the humor. However you are going to need to start trimming out unneeded scenes in order to keep the pace up or you, and your readers are going to continue to loose interest.
Either that or put the comic part to one side and start using a word processing program. I have seen those quotes you put in so I know you can write. Type up a whole long scene all at once and put some well done pictures in. It may sound silly but I'd rather get a whole scene of plot and one good picture of Tessa, than 1/20th of a scene and 4 so/so pictures.
Well. That's my 2 cents worth. Sorry if it wasn't as reassuring as you were asking for