、。
We agreed on too much, which actually made me suspicious.
Literal
Talk [subject-が] match too-much [because-ので], on-the-contrary something suspicious [quotative-と] thought.
話が合う ('to agree, get along in conversation') + ~すぎる creates a paradox: too much agreement breeds suspicion. かえって ('on the contrary, instead') is a key adverb marking an unexpected reversal — the good thing (agreeing) produces a bad result (suspicion). A psychologically acute observation.