18 month old toddler tantrums in stores! Please help! I feel like I'm losing my mind 😭

I feel like a terrible mom for even saying this, but I feel like I'm about to lose my mind some days 😭 my son is about to be 18 months old and number two is on the way. The tantrums are terrible and they mainly occur in stores 😞 I do not give in and I ignore it the best I can. There's no sense in it and it's so frustrating & embarrassing! I always make sure he's fed, well rested and had a drink and bring one before we go and usually bring a toy or find one in the store and let him play with it while we are there, and he still does it! 😤😥 he usually throws the toys after awhile and starts his tantrums after I won't give them back after a few times of throwing them, and once he starts a tantrum I ignore it and I hide whatever he's throwing a tantrum about (out of site out of mind) . any advice would be appreciated, I feel like I'm going to lose my mind when this happens and pregnancy hormones on top of it don't help! I usually just end up leaving everything at the store and leaving cause he won't stop and it's so embarrassing 😩happened again just now. 😭