What should I do if I take low dose birth control pills and I bleed in the middle of my cycle?

Change pills. The average dose of estrogen in most pills is equivalent to 30 or 35 micrograms of ethinyl estradiol. The "low dose" pills have only 15 to 20 micrograms - sometimes they are better tolerated in regard to nausea and headaches, but the downside is that there is a much greater frequency of breakthrough bleeding. There is also a greater risk of pregnancy. You should discuss a change with your doctor.
Midcycle spotting. Best discuss this with your doctor. Perhaps you need a change in your birth control pills if this continues.