Carb counting whey protein

Hi,
I've been going to the gym for some time and always used to take some whey protein isolate after my sessions which were mainly resistance based. I used to take the protein & a banana. The protein has the following carbs:
1.8g per serving or 5.8 per 100g
I would take 2 servings and banana. I was counting this(incorrectly I believe) as 1.8g x2 =3.6g + 2CP for banana = 5.6 CP. As I was just after exercise I used to take 4 units of novo rapid and this always worked out well, no hypo or high readings.
Now I believe my above calculation for the CPs in the protein was incorrect. I've also changed to taking some protein pre workout. The total amount of carbs in grams I have pre and during workout is 7.2 grams. I calculated this as 0.72CP. Having a reading of 8.0 pre workout this morning I consumed this without any novo rapid as I didn't want a hypo during the session. Afterwards my reading was 17.3.

What did I get wrong?!? My maths? Or is this because all the carbs were all liquid based and therefore took effect quicker?

I'd appreciate any advice.

Thanks, L.

When I exercise (which is first thing in the morning) I eat a banana before I go to the gym which is about 3.5cp. I normally run 9k in 45mins and during that time I drink an isotonic drink which is 1cp. I then do weights different parts of my body on different days ( I go five days a week). I then as I leave the gym have a protein shake 2cp. I only inject my background before going and don't inject any quick acting. Sometimes when you do to much weight training it can raise your bloods. When I have breakfast I don't usually adjust I just inject for the cps I'm eating. This is because in the past my bloods have crashed down by lunchtime causing me to have a hypo. Hope this helps your query. GMac

I tend not to do my cardio in the gym, just weights so you could have a point here alright. A bit if trial and error since and I'm getting closer to where I want to be now.
Thanks Gmac.