A bit nervous...

So, I've gotta disclose some background info first. Around early October I ended up in the emergency room for an injury, which I was then told I was a week or so pregnant based on my hcg, however I had the Skyla IUD in place for a year and a half. They removed the IUD and I miscarried the next day, but needless to say as someone who's never been pregnant before it was a very stressful/scary experience. There was no IUD failure that my ob/gyn could determine, and I was just told I happened to fall into that .01% chance statistic. About a month later I had Mirena implanted instead. All went well and I adjusted to it fairly quickly with a pretty normal period my first cycle, just frequent,normal spotting. Fast forward 2 months and that brings me to my issue now. My last period lasted for 15 days and I spotted frequently after that as well. Now I haven't spotted for probably 2/3 weeks and my period for January is 10 days late. On the Skyla IUD my periods never stopped and I was never late. I'm starting to get a little nervous and my husband is definitely uneasy, especially given our previous experience. I've done multiple string checks and everything seems in place and my CM is thick. However while I've never been this late before, I also had all that abnormal spotting and bleeding last cycle so I'm not sure what's going on. Should I start heading to the store for a pregnancy test or give it a bit more time? Thanks in advance for any advice!