I think you should not worry. Insulin is a Master Hormone in the body and it affects ALL the other hormone levels.

When we start LCing, we drastically lower the insulin level in the body and switch to the other Master Hormone, glucagon, to process food for fuel AND take fat out of storage.

It is ENTIRELY USUAL that a woman's cycles are out of whack for at least the first month of LCing.

One could, for example,:
-skip a period
-have a heavier or lighter period
-have an early period
-have an extra long period

Wait until the second period should have started and see how things go. IF you are staying totally on the LC plan you have chosen, then things are VERY likely to go back to normal.

If, after 3 months of LCing, things are not normal, OF COURSE consult your doctor.

As you are on LC, you will not be drinking alcohol and you will be taking supplements of vitamins, so you won't be doing anything bad if you should happen to actually be pregnant.