You should have had a CRP test before, as it's one of the standard blood tests for inflammation. There's a small % of people for whom CRP is completely inaccurate; their CRP doesn't rise even in the middle of a flare-up. But for most folks, if they have inflammation anywhere in the body, an elevated CRP will reflect that.
Faecal calprotectin is a rarer test and so there's a good chance you won't have had it before. That's more specific than CRP, in that it measures the level of a protein called calprotectin that can only be found in the intestines, nowhere else. It's often used to distinguish between IBS and IBD during the diagnostic process (calprotectin isn't raised in IBS). But it can also be used as monitoring tool, like the CRP, ESR, and other markers.
Unless you know your previous results, getting a CRP test done now won't tell you a lot. It's more useful when you have a baseline to work from, i.e. comparing current CRP to past CRP results during flare-ups.
Good luck with the Stelara. It works differently to Remicade, Humira and Simponi, so hopefully you will have better luck with it.
Dx Crohn's in June 2000. (Yay )
Tried: 5-ASAs, azathioprine, 6MP, Remicade, methotrexate, Humira, diets.
1st surgery 20/2/13 - subtotal colectomy with end ileostomy.
2nd surgery 10/7/15 - ileorectal anastomosis. Stoma reversed and ileum connected to the rectum.
Current status: Chronic flare. Do I have any other kind?
Current meds: 50mg 6MP; Entyvio (started 3/11/16)