Fenwick was born in Gateshead, Tyne and Wear. He played for Newcastle United, Sunderland and Middlesbrough academies before joining Gretna in 2009. He left the latter in the same year, and subsequently joined Newcastle Benfield in 2010. In August 2012, Fenwick signed with Durham City, scoring 18 goals from 32 appearances in his first season and 33 goals from 41 appearances in the second. He moved to fellow Northern League team Dunston UTS in June 2014, and scored 13 goals in all competitions, of which 7 came from his 12 league appearances.
Hartlepool United
On 7 November 2014, Fenwick signed an 18-month contract with Hartlepool United. He made his professional debut eight days later, replacing Matt Crooks in a 1–0 defeat against Southend United. Fenwick was handed his first start on 22 November 2014, and scored his team's only goal in a 3–1 defeat at home to York City. Fenwick scored three goals in five matches during January 2015 against Cheltenham Town, Tranmere Rovers and Plymouth Argyle and formed a good partnership with strike partner Rakish Bingham to help Pools get their first wins for three months. Unfortunately for Fenwick, after scoring Hartlepool's only goal in a 3–1 defeat at home to Stevenage on 14 February, he was ruled out for six weeks with an ankle injury. He returned in time for Hartlepool's relegation battle and scored the opening goal in a 2–1 win against Exeter City which confirmed Pools' survival. Fenwick started the 2015–16 season partnering Rakish Bingham and Billy Paynter up front, helping Hartlepool win their first four matches and scoring the winner in a 1–0 home win against Newport County. Despite scoring against Newport, Fenwick was dropped for Rhys Oates but returned for the Football League Trophy match at home to Sheffield United, scoring Pools' equaliser but missed a penalty in the shoot-out. Fenwick was once again dropped to the bench but returned against Yeovil Town to score Pools' opening goal in a 2–1 away win.
York City
On 4 July 2016, Fenwick joined newly relegated National League club York City on a one-year contract, with the option of a second year. He made his debut when starting their 1–1 away draw with Maidstone United on 6 August 2016, in the opening match of 2016–17. According to Dave Flett of The Press, Fenwick found the "going tough in attack", and was substituted for Richard Brodie in the 84th minute. He was an unused substitute as York beat Macclesfield Town 3–2 at Wembley Stadium in the 2017 FA Trophy Final. He was released by York at the end of the 2016–17 season.
Later career
Fenwick signed for National League North club Darlington on 4 August 2017 after a successful trial. After making four substitute appearances in 25 days, he left the club by mutual consent. He signed for Maltese Premier League club Naxxar Lions, and made his debut on 10 September 2017, starting in a 0–0 away draw with Valletta. After four goals from twelve league appearances and two goals in the Maltese FA Trophy, Fenwick was released by mutual consent on 2 January 2018 because he wanted to return home. Fenwick signed for National League South club Chelmsford City on 9 March 2018. He scored a hat-trick of penalties for Chelmsford on 9 April in their 4–2 win against Whitehawk, becoming the first player in the history of the club to do so. Five days later, Fenwick scored a hat-trick of penalties for the second consecutive match, scoring all four Chelmsford goals in a 4–2 win against East Thurrock United. On 13 May 2019, Chelmsford announced the departure of Fenwick. On 14 June 2019, Fenwick returned to North East England, signing for Blyth Spartans.
