Dear An: The easiest question first, OK? Severe itching of the vagina and/or vulva can often be linked to a bad "yeast infection." In addition to the itching, yeast can create inflamed vaginal tissues which makes sex super uncomfortable. Some other causes of itching can include contact dermatitis (allergic response to bath product,laundry product,etc.), sanitary pad irritation, or some autoimmune conditions (eg lichen sclerosus, lichen planus) or even atopic dermatitis. You could choose to try an over the counter treatment for yeast. Consult with your pharmacist for their product recommendations--some products do not have the best anti-fungal ingredients.
In terms of the erratic bleeding pattern, breakthrough bleeding (BTB) can be a common side effect of most types of hormonal birth control (eg pills/patch/ring/shot/Mirena IUD). Among birth control pill users BTB frequently occurs after a missed or late pill. In your case it sounds like you are careful to take pills at the same time daily.
When a woman uses hormonal birth control it can make the lining of the uterus more unstable--so it is easier to have some of it begin to shed. Sometimes the lining is less stable because the hormones make the lining much thinner (actually this is good as a thin lining is a healthy lining). This is the more common reason in a longer term Pill user. Sometimes the lining is unstable because the hormones can make parts of the lining out of synch. Fortunately, having a two week period when one is using hormonal birth control is not as worrisome as a woman with a two week flow who is not using any hormones.
Bottom line, BTB on hormonal methods of birth control is a nuisance side effect. The protection from pregnancy is still in effect. If your poor cycle control persists you should return to your GYN or clinic. Often a change in the brand, or formula, of birth control pill will fix the problem. Two weeks a month of BTB is not good cycle control.
I would suggest that you go back to your OB/GYN to get checked for the cause of the vaginal itching. At that time ask her about changing to a monophasic (same dose each week) type of pill. If you had a pill which you used successfully before you could request a change back to that brand/formula.
Yours,
Jane