Ay, ganyan din nangyari sa akin dati, nakakaalarming feeling talaga! Since it comes and goes, pwedeng ligtas lang na gas or muscle strain, pero since you're pregnant (I'm assuming based on your concern), better to mention it sa OB mo sa next checkup para sure, lalo na if it happens again or gets worse, hindi magugol ng malaki, at peace of mind lang talaga worth it.