Yes, diet is critical. Don't know what you eat, of course, but it's quite difficult to cover very high carb meals with insulin. Absorption rates are variable with larger insulin doses & the chances of miscalculating increase. The result is what you're experiencing with highs & lows.
The other obvious answer is to fine tune your doses & try your best to be accurate with carb counting. Protein also effects BG, though we're rarely told this. About 58% of protein converts to glucose, so people should calculate that into bolus dosing.
Do you see patterns in your highs and lows, Chinu? You might have to do some tweaking of doses. If you are having problems with your post prandials then you should consider altering your I:C ratios. If you have problems with your fasting, in between meals and at bedtime, then you might want to tweak your basal rates, giving yourself more or less for different time zones.
I agree with Gerri, if you are eating a lot of carbs that makes it harder to get predictable results.
Try making some small changes in diet and insulin dosing and see what happens. Perfection isn't much of an option for most of us, but we all have room for improvement!
There is also the impact of the female period to consider. I would recommend to write down the beginning of the cycle and your current day in the cycle. So on the first day you write 1 and count up for the following days. The idea is to identify the pattern how the hormones are influencing your glucose. With some hormonal levels your sensitivity to insulin will decrease with other levels it will increase. The idea is to increase or decrease the basal rate according to the cycle. For example to increase the basal in the week before the menstrual bleeding which marks the restart of the cycle. Some of our users in our Glucosurfer project explicitly asked for a feature to track these changes - as you can see here:
Trial and error I suppose. Perhaps you should ask other women how they handle their recurring patterns effectively.
Diet plays a critical role. If you can maintain consistency in carb/protein content for each meal each day, you can remove most of the variability that food plays and then fine tune your insulin accordingly.