There's not much you can do until you reach higher levels.
There are two level-one spells on the magus spell list that will both increase your reach by 5 ft. Long Arm increases your reach by 5 ft. Enlarge Person increases your medium sized tiefling to large giving you a 10 ft reach, +2 Str, -2 Dex, -1 AC, and 2d6 damage. Combined they can increase your reach to 15 ft. Casting spells is the best thing your 14 Int, 6 Str magus can do. With only 3 level-one spells to cast each day and pathetic melee abilities, I wouldn't recommend using spell slots for either of these spells until you have gained additional levels and the spell slots that come with them.
The Longarm Bracers (7,200 gp) can increase your reach by 5 ft at the expense of a swift action every turn and a -4 penalty on weapon attack rolls. You can't afford a penalty on attack rolls and are going to need your wrists magic item slot for something else.
At 7th level you can improve the reach of your touch spells by 5 ft during your turn (at the cost of 2 AC) by taking the Lunging Spell Touch feat.
At 9th level you can improve your reach by another 5 ft during your turn (at the cost of 2 AC) by taking the Lunge feat.
If you increase your Cha to 15, take Skill Focus (knowledge (dungeoneering)), and take Eldritch Heritage (Aberrant) then at 11th level you can take Improved Eldritch Heritage (Aberrant) to get the 3rd level power of the Aberrant Bloodline. This increases your reach by 5 ft when making melee touch attacks. Besides your touch spells, there are various whip-themed spells that allow you to make melee touch attacks, though you may need to pilfer another class's spell list to get them.
If you do all of the above your melee attacks can have a reach of 20 ft at level 9, your melee touch attacks can have a reach of 35 ft at level 19, and your touch spells can have a reach of 40 ft at level 19.