Insulin

So I'm type 1 diabetic (the one not caused by sugar and obesity) and therefore insulin dependent. I've noticed that since I started this journey, even my baseline sugar levels have been sort of all over the place.

For example:
This morning my sugar was 152. I did my baseline insulin (lantus). I then had my fiber one breakfast bar. I didn't take any insulin to cover the breakfast bar.

At lunchtime, my sugar was 52, despite the fact that I did not give myself any insulin to cover the fiber one bar. It should have been high, not low.

I haven't exercised this morning outside of my usual 10 min walk from the metro to the office.

So sometimes it happens like this, or sometimes I'll be high even though I haven't eaten...

So my question: can the type of foods I'm eating, or the fact that I've been increasing the amount of exercise I'm getting (though I didn't last night), cause random spikes and/or drops in insulin levels for someone who is regulating the amount she is taking (ie, not just producing it naturally to cover what she needs)? I'm sort of confused as to why I'm getting these random, unexplained readings.

I plan to ask my dr. next week, but just wondered if anyone here had any insight.