Would you find it odd if your partner deleted texts all the time?
How about if it started off where he only deleted certain texts (like only certain people and then parts of conversations etc) and then when you pulled him up on it he said it was to save space and then made a point of deleting all texts? How about if you know full well he's been texting his ex wife and on occasion, a woman from work and those texts are not in the history?
How about if he kicks off about you receiving texts from other man (just male friends) and then when you retaliate with "at least I don't delete my texts" he goes quiet and suddenly changes the subject?