Borderline diabetic?

It's difficult to say, no-one here can diagnose you from a few random blood tests. You should make an appointment with your GP and get him to send you for some tests.

A few observations though:
How high has it been? I doubt that you'd get the whole "dizziness, shaking, thirsty, tired" thing a 7.9 mmol/l, most of us have BG readings >10mmol/l before we are diagnosed (mine were at 24.4 mmol/l). While not ideal, 7.9mmol/l isn't very, very high.

Diabetes has more to do with carbohydrates than sugar (sugar being just one form of carbohydrate). (Nearly) all carbs turn to sugar in your blood, and from that point of view a big plate of pasta is one of the worst foods you can eat (along with bread, rice, potatoes and anything with flour or sugar in it).

It also depends when you test, everybodies BG rise after they eat carbs. The question is, do yours come down to reasonable levels? It sounds a bit like they don't, but you really need to test 2 hours after eating, because if you test straight away they can be deceptively hight.

Go to the Docs. Most of the symptoms you describe are probably down to worrying.