No its not.
(1)There is no doubt that this is an act of zinaa, because the Prophet said: “The eyes may commit zinaa, the hands may commit zinaa, the feet may commit zinaa and the private parts may commit zinaa.” [Imam Ahmad, 1/412; see also Saheeh al-Jaami', 4921]
(2)Ibn Umar radhiAllahu anhu reported that the Prophet said: “From this day on, no man should enter upon a woman whose husband is absent unless there is another man or two with him.” [Muslim, 4/1711]
(3)The Prophet sallAllahu aalyhi wa sallam said: “If one of you were to be stabbed in the head with an iron needle it would be better for him than touching a woman whom he is not permitted to touch.” [Tabaraani, 20/212; see also Saheeh al-Jaami’, 4921]
I see satan has already succeeded in convincing you that haram is halal. Emotions can't make wrong right nor change Allah's law.
“Tell the believing men to lower their gaze (from looking at forbidden things), and to protect their private parts (from illegal sexual acts, etc.). That is purer for them. Verily, Allah is All-Aware of what they do.” [al-Noor : 30]
Why don't you do Nikkah instead and Rukhsati later? But no one heeds to commandments of Allah, and remember Allah won't give heed to you on the day of Judgement.
You have committed zina anyway without penetration.
The punishment of those who die without repenting from zina begins in their grave. In a long hadith, Allah’s Messenger (s.a.w) related a dream in which he saw two men accompanying him (Jibreel and Maalik), showing him how a number of sinners were being punished in al-Barzakh (life between death and Judgement day). The Prophet (s.a.w) said: “…We proceeded until we came across a hole in the ground that resembled a baking pit, narrow at the top and wide at the bottom. Babbling and voices were issuing from it. We looked in and saw naked men and women. Underneath the pit was a raging fire; whenever it flared up, the men and women screamed and rose with it until they almost fell out of the pit. As it subsided, they returned (to the bottom). I said: ‘Who are these?’ They said: ‘…As for the naked men and women who were in the pit, they are men and women who indulge in zina…”(12) In a similar narration Allah’s Messenger (s.a.w) said: “We moved on until I saw people who were awfully swollen, and had the most foul stench, their stench was like that of the sewers. I asked: ‘Who are these?’ They replied: ‘Those are the male and female adulterers.’”(13) As for punishment in the hereafter, Allah Most High says: “And they (i.e. the servants of Allah) do not commit zina - And whoever does this shall meet a full penalty. The torment will be doubled to him on the Day of Resurrection, and he will abide therein in disgrace.”(14)
At least have mercy for the woman you love. Don't drag her to hellfire as well. Marry her if you love her but don't ruin your hereafter.
"O you who believe! Let not your properties, nor your children divert you from the remembrance of Allah. Whosoever does that, then they are the losers. So spend (in charity) of that with which We have provided you, before death comes to one of you and he says: ‘My Lord! If only you would give me respite for a little while (i.e. return to the worldly life), then I should give Sadaqah (I.e. Zakat - Obligatory charity) of my wealth, and be among the righteous.’ But Allah grants respite to none when his appointed time (death) comes. And Allah is All-Aware of what you do."
(Qur'an Al-Munafiqun 63:9-11)