Two options I can think of:
- As suggested in this answer you can see a "raw" summary of your reputation if you go to (in this case Worldbuilding) the following link: https://worldbuilding.stackexchange.com/reputation
Here you can see a detailed report on the reputation you have gained/lost, the days you have repcapped, etc. You can also "see" the reputation you "lost" (or that you didn't gained, that is) in there; they will be the ones surrounded by brackets, similar to
[x] (where x is the portion of rep you gained that the cap didn't truncate).
- On your user profile, under the Reputation tab you can also see a detailed drop-down report where you can see the Rep gained on each day, per post. There you can see all votes you have received, some of those will have no
+10 associated, meaning they were votes you received after the repcap. For example, let's see this screenshot I took from last time I capped:
We can see that the vote on top didn't add any reputation to my profile. We can see that the one in the middle only added
+3, probably because I was 3 away from earning 200 reps. The last vote was before the cap and had it's full value added to my rep. If we compared those votes with option 1, they would show
Edit: You can also try the SEDE query linked by @SOLO in comments: How high would my reputation approximately be when there was no cap or CW?