Given your description of clitoral pruritus (itch), absence of erythema (redness), edema and other changes , and recent unprotected intercourse, it seems that you might be experiencing a kind of bacterial or other infection, vulvo-vaginal candidiasis, UTI-urinary tract infection, sexual-hormone changes or even an allergy to that oatmeal lotion (the reason could not be confirmed without an examination). Any kind of pro-biotic over-the-counter gel applied locally (available in pharmacies) in combination with sitz baths and oral pro-biotic yogurts might solve this unpleasant problem. It will help by restoring normal vulvovaginal flora. If this does not solve the problem, you could try with an OTC anti-fungal preparation (3 or 7 day vaginal tablets in conjunction with an anti-fungal vulvo-vaginal cream, for a longer period). Combining them with a cheap anti-itch corticosteroid OTC cream is always a possibility. Moreover, vulvovaginal hygiene is an imperative. But only with warm water, at least once daily, without overwashing the vaginal area (no usage of soaps, gels or lotions is recommended, because they could provoke vaginal pH disbalance). And always dry that area thoroughly-this is very important.

However, you might want to visit your family doctor or gynecologist, who might do a pelvic examination, take swab samples, urine culture and/or do laboratory tests for sexual hormones, if necessary. S/he might even add allergy tests for oat or other components of that lotion you used (you might stop using it, at least for a while). If it is a urinary problem, you could start drinking plenty of cranberry juice or take cranberry extract capsules and consider seeing a doctor for further advice.

Finally, condom usage would be most advisable.