Matthew Parsons, aged 36, a lorry driver and plumbing and heating engineer, from Kemsley Drive, Leighton Buzzard, appeared for sentence having pleaded guilty to sexual assault on a female.
After the woman reported the assault, officers arrested him.
Parsons told police he had downed more than eight pints of lager before the incident, Luton Crown Court heard.
In a victim personal statement the woman said she was "sick to her stomach".
“I have no escape and no opportunity to forget what happened. I’m plagued with tension headaches and palpitations, and now have a fear of being alone,” she said.
“I dread having a shower. I won’t do it unless there’s someone at home with me. The second I get in I’m scared a stranger will come into the house. I don’t close my eyes anymore when I wash my hair because I don’t want to risk those three seconds of not being ready to defend myself if someone walks in.
“I used to sleep well. Now I wake up most nights paranoid. When I hear a noise, visions come back of that night, waking up seeing that man’s face in my bed. Some nights I’m frozen, unable to move through the fear. Some nights, I have so much energy from being in constant survival mode, I’ll get up and check every door in the house is locked and that there is no one else in my home.
“I believe he targeted me that night as he believed me to be an intoxicated single woman with no one else in my house.
"I will never truly know what he did to me before I woke up, it plays over and over in my mind and makes me feel ill.”
Defending, Oliver Kavanagh said: “He said to the probation officer ‘She will never forget what I did.’
“He has no previous convictions, made early admission and has shown genuine insight and remorse."
He said Parsons, who also coached young footballers, had the benefit of a supportive but a very disapproving partner and family.
Investigating Officer Gillian Cook-Smith said: “This whole experience has left the victim, a once confident and independent woman, understandably traumatised.
“I would like to commend her for the extraordinary bravery she’s shown, not only in reporting this to us, but also in providing a hugely powerful victim impact statement and having the courage to read this out in court.
“This kind of behaviour is completely unacceptable. Parsons clearly made the assumption that the victim was heavily intoxicated and took advantage by creeping into her house whilst she slept and getting into her bed before touching her sexually.
“I really hope that this outcome will give other women the courage to report such incidents to the police. Please know that all reports will be dealt with and investigated fully and we will do everything we can to support victims and see perpetrators like Parsons behind bars.”
Parsons reportedly cried in the dock when sentence was passed by Judge Rebecca Herbert.
He must register as a sex offender for 10 years.