Spotting for 3 weeks! 9 weeks 5d pregnant

Okay so i had my son in December 2018 rainbow baby! ❤️. found out i was pregnant. Again at 3 months pp They’re going to be 12 months and 12 days apart! Wooohoo but I’ve been off and on spotting for 3 weeks! I did get pregnant on birth control and just didn’t know if that could be why? I’ve been to the dr constantly had 3 ultrasounds to figure out why and they can’t find a SCH or any reason as to why cervix are high and super firm just curious if anyone else has had these issues ??? I’m literally losing my sanity here!