Had itchy bumps for a week now after going biking w/ sunscreen. seem to be clear/flesh colored until i scratch them and they turn red. is it heat rash?

Maybe: It is possible, depending on location of the bumps/rash. Areas under clothing or heavy perspiration are potential sites for such rashes. If on outside skin areas where sunscreen was applied, may be assoicated with contact allergy to the sun lotion or its preservatives contained. Do not scratch them. You may try use of 1% hydrocortizone cream (cortaid) applied 2-3 times a day... No scratching.

Heat, drugs, etc: There are a variety of possible causes for this including photosensitivity induced by systemic drugs such as bactria, contact dermatitis due to a reaction to the sunscreen or, yes, heat rash. In the latter case it will likely be limited and short lived. In the former, you should determine the cause. In the meantime consider topical Benadryl (diphenhydramine) and Hydrocortisone for short term relief.