2.5 yo speech delay

My 1st boy has always been behind in speech. We had him evaluated at 18mo Bc he only said mama dada. They determined he was at a 9mo level in expressive speech. He scored high on everything else and was diagnosed with a expressive speech delay. We went twice a week for 6 mo and saw some improvement but it was so small we stopped going. I sat in every session with him from the first to last and I do at home what they did there. It’s now been 5 mo at home and I still feel like he’s so behind. He’s very smart but he likes to babble in his own language. He know all his letters (can point out every single one on a puzzle or book and say it), knows how to count 1-10, knows tons of animals and sounds and lots of food etc. he seems like he wants to talk. He gets super frustrated Bc he can’t communicate his wants or needs. I just don’t understand why it’s not happening. He says “here you go and ready set go” as the only connected words and that was from copying. He seems to be a visual learner as he tries to copy songs or tv but he doesn’t come up with words or phrases on his own. We only have that one speech place in my area and I feel like he’s made more progress with me. Is anyone else in this boat ? He has no signs of autism and they didn’t suspect apraxia at the time so why is he still barely taking 1 year later? I just don’t understand ;(