Jaq Martin was given a restraining order to keep him away from his former partner after he was convicted of battery, for spitting in her face, in April last year.
Newcastle Crown Court heard on February 16 the 23-year-old contacted the woman from a private number and accused her of seeing someone else.
She told him to leave her alone but he called ten times within eight minutes and sent an email warning "I will do any ******* amounts of damage".
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He then persisted in his bid to speak to her.
Prosecutor Rachel Glover told the court: "Between 7pm and 10.22pm she received 100 phone calls and 10 emails."
The court heard two days later she received two more emails, asking "please speak to me" and requesting to see their son.
On April 9 she received five missed calls from an unknown number.
When she answered as it rang a sixth time Martin was on the line and "screamed sorry at her" before she ended the call.
In a victim statement the woman said: "I am genuinely scared of this man.
"I will not be able to feel relaxed until he has gone from my life.
"I am scared of what he might do.
"It's like he's obsessed, I just want rid of him. I am scared of him. I just want to be able to live without being in fear."
Kate Barnes, defending, said Martin is a "articulate and hard working" man who has a good employment record and university place and is "desperate to get back on track".
Miss Barnes said Martin, who had been trying to make child contact arrangements with the victim, has been the subject of physical abuse while in custody on remand and is "desperate to get back out".
Martin, of Tel El Kabir Road, Sunderland, admitted breach of restraining order and breach of a suspended sentence he was given for driving offences.
Judge Stephen Earl sentenced him to a total of 18 months behind bars with a two-and-a-half year restraining order.
Judge Earl said he "repeatedly, persistently and seriously" breached the order to stay away from the woman.