All three forms are perfectly valid and mean the same. There's no special reason to prefer one over another. The present tense is fine - if there's a failure of comprehension, it's still ongoing. Past tense is also fine, and either auxiliary verb is just a stylistic choice.
But I personally wouldn't use ""catch the meaning in OP's context - I'd just say "...if you didn't understand me". We normally say "catch my meaning" when referring to something we just said, but usually this is in a context where what we said was deliberately obscure for some reason (perhaps something "conspiratorial", or otherwise sensitive). It's an odd expression to use after having phrased something badly because of inadequate skills in a foreign language.