Is my boyfriend cheating... or did he? this cant be coincidence...odds are not in his favor. proof or faith?

relationship of 10 months for us. he broke up with "jess" in december. i never even knew she, or that relationship, existed until recently. around june- i found tank top and thong, not mine, in our new apt. i still stay at home sometimes tho. around beginning of july-she came to my work on my day off-got a brochure- and placed it on my b/f's windsheild. i was in the apt. he was running out to the store. he came back, and explained to me it had to of come from "jess" cuz she found out about me and him and how serious we are just days before. "she's crazy and obsessed" he said. also informed me she and her friends are known for jumping people and have criminal records. well- i stayed calm. i got her last name just in case. which was very hard to do. things calmed down- she called him cuz she was worried id called the cops- end of that. until beginning of sept. his cell rings at 1 am. he "doesnt know the #". i call it in the morning- first time ive EVER looked at his phone. it rings,then the recording "hi, youve reached the *ex's last name* residence...". i take down the #. confront him. he"cant control who calls him". i talk to her 2 days later and she tells me what type of sheets are on his bed. that i bought. what my make up case looks like. he claimed my stuff was his lil cousin's. i found my stuffed bear in the closet once too. other things of mine hidden. she told me they were together for a year. she doesnt sound psycho. she came to my work cuz she thought i knew about her. he tells me she tried to buy a car from him a while ago. they also went out for drinks one night. 1st- with her and friends. later-just with her. 1st-she had to pee, and saw my stuff. later-he wanted to show her his new furniture. he also mentioned he thought she was coming on to him at the bar...