2 weeks into lexapro, i am exhausted

Just as a side note, i(26f) have severe ADHD and i’ve never been on SSRI’s before. I have been taking Concerta (a stimulant) since March which works alright to help me focus and stay on task and not entirely fall apart with my busy stressful life but as i get older i have developed a lot more anxiety and i cry a little too much lol. So my psychiatrist put me on 5mg of lexapro on top of the concerta i take approx 4-5 times a week to alleviate some anxiety and high emotions i experience. I know you are supposed to feel the full side effects 4 weeks in but right now, 2 weeks in all i feel is exhaustion. Not even the concerta can wake me up and get me feeling alive anymore. I am yawning all day i feel so tired and sleepy and im pretty sure its the lex. I was told to take it in the morning but would switching to taking it at night help? Does anyone have any advice ? Does it get better ?