Syphilis tpha varies/ or cross reaction?

Im married in 2017 and got pregnant. At 8 weeks Blood tests showed vdrl positive. Tpha - negtive 0.2. Husband was tested vdrl positive and tpha reactive 1.8. Since i was negative i was lethargic. At 12 weeks i wanted to ensure again and found tpha 4.51. I consulted physician and took 3 doses of benzathine penicillin after 19 weeks only. Thankfully my son born safely without complications. My husband took 1 dose of b. Penicillin. Is 1 dose enough? We both do not have any symptoms. May be this is cross reactivity? After this many years, we have a conspiracy that i acquired infection and spreaded it to him he suspects and big issue is going on. I swear that i dont have any sex exposure before marriage. With the titers is it possible to let him know who had the infection first?