なぜかうまくいかず、目下全戦全敗、「彼女いない歴＝自分の年齢」という寂しい生活を送っていました。

、、「」。

For some reason it just never worked out — currently a perfect losing streak, living the sad life where 'girlfriend-less years = my age.'

Literal

Somehow well-go-[not-ず], presently all-battles all-defeats, 'girlfriend non-exist history = self [gen-の] age' [quot-という] lonely life [obj-を] was-sending [polite-ました].

目下 (もっか) is a formal adverb for 'presently / currently / as of now.' 全戦全敗 is a four-character compound ('all battles, all defeats') — a sinitic parallel construction of the form seen in many 四字熟語. 'いない歴' is an internet-era idiomatic suffix: 歴 'history' attached to a negative state ('not-having' history) to form a mock career label — 彼女いない歴 'girlfriend-less-years.' ~を送る 'to send / lead (a life).'