OK, irregular cycles do make it more likely that there can be a discrepancy between the scan date and last period dates, so there is some hope there.
Having said that, the big decider for me is usually the date of the pregnancy test. This is because it is possible to ovulate/implant really late in a cycle, but if so there would not be a positive pregnancy test until a correspondingly later date, because the embryo would need to have implanted to start producing the hormone the test needs for a positive result, if that makes sense.
If you tested on day, 30, and got a clear positive, this would suggest to me that the earliest date you could have been, was about day 23/24 as it is not possible to get a positive before this- that would adjust your date backwards to place you at about 8 weeks, so it is concerning that you are showing at slightly less than 6 weeks.
Unfortunately in my experience when this has happened to me a couple of times it has not gone on to be a successful pregnancy in the end.
If I was in your situation I would be hoping for the best, but preparing myself for the worst just in case. It is horrible to have to write that, and I hope I don't hurt you by saying it, but for me it was better to know that it indicated that there was an issue than to not be prepared and for it to be a complete shock if it happened.
I have to say for me the waiting is absolutely the worst thing, that combination of naturally wanting and hoping for the best and fear that it won't happen that way is a special kind of torture.
What plans have they suggested they put in place? Do you have an appointment for a rescan? Is it in a week?