I get jealous easily anyway to fix that?

My boyfriend and I have been together for a year and a half and have an 8 week old together. I do not trust him and I snooped through his phone for the first time yesterday and found things don't know if I believe him or not, he had text messages from a random number saying "text me when your home so we can um..." with a link going to a blow job site, and some other provocative texts from other numbers. I asked him he said it was spam mail (I didn't think spam mails got sent as text messages from numbers) and we got into and argument about trust and stuff,I'm probably overreacting but needed to vent. Should I believe it's spam? Does it sound fishy? And what helps Not get jealous?