The 40-year-old TV presenter was found dead in her apartment on 15th February 2020, having died by suicide.
Taking to Instagram on Monday, the 27-year-old wrote: "It's already been a month I love and miss you so much, I never thought that one day I will never be able to see or speak to you again."
The former professional tennis player went on: "I wake up and think you're going to be laying next to me or you're going to call me in a minute. It just doesn't seem real. I wish I could give you a kiss and a cuddle and say everything is going to be ok."
He ended his post by saying: "I am so grateful I met you I just want to make you proud. X"
Alongside his sweet tribute, Lewis - a model - shared a series of photos of him and is late girlfriend.
Caroline was found dead at her east London home on Saturday 15th February.
The Love Island host was due to appear in court after being charged with allegedly assaulting Lewis - something both parties had since denied.
Lewis and Caroline were banned from speaking to one another ahead of her trial. Lewis did not want to press charges but the trial went ahead.
Before her death, Lewis had spoken out in defence of Caroline, saying he was "tired of the lies and abuse" aimed at her.
The day after her death, Lewis wrote on Instagram: "I am so lost for words I am in so much pain I miss you so much I know you felt safe with me you always said I don't think about anything else when I am with you and I was not allowed to be there this time I kept asking and asking.
"I will be your voice baby I promise I will ask all the questions you wanted and I will get all the answers nothing will bring you back but I will try make you proud everyday."