@Tuddy I'm a tad confused as to your type as your profile shows T1, but you've posted this in T2 with insulin? It also helps to get better answers if you give as much information as you can. People can only stab at suggestions from such a brief description.
The insulin you're on is a mixed/combination insulin, so there are a number of issues that might be at work here. I'm a T2 treated with insulin and have had to come off the combi insulins as the proportions and profiles of them didn't suit my personal patterns. I did really well on them for about 10 months, then once I had good control, the profiles no longer suited. The profile of the insulin is usually expressed as a graph that shows when that insulin peaks in your system, how long it lasts and when the effect runs out. The combination insulins have two peaks that overlap, one diminishing as the other takes over.
I've not been on Humulin M3, but I understand that it's a 30/70 mix of short acting and basal insulin, much like the NovoMix I've just come off, except I think the Humulin M3 has a much slower profile - the bolus aspect is fast acting, as opposed to rapid.
It could be that, like me, the profiles of one of the insulins within the mix doesn't work well for your eating patterns and the speed with which the insulin works in your personal system - because a combination insulin taken twice a day is always a best guess dose for the next 12 hours.
For me, we decided that the basals in the mixes were staying in my system too long, but I wasn't getting enough 'bolus' to cover meals in the combination therapy, so I'm just starting separate insulins, so that I can tweak the ratios to suit me better.
You need to have a conversation with your DN to get to the bottom of it.