You picked wrong 'un in your secretive ex and that fact alone can be a confidence shaker.
However, as that relationship is long gone, any resultant negativity can only adversely affect you as long as you allow it to.
In any new relationship it is not necessary to place your wholehearted trust in the other person from the off. Trust happens by degrees and your trust in other people should be incremental and based on your observation of how they behave towards you and to others.
Obviously, simply going out with a person who is previously unknown to you or to your friends/family implies a degree of trust in that you are trusting to your own judgement that they're not completely psycho and you won't end up swimming with the fishes after a night at the cinema.
To this extent, in the very early days it's necessary to take certain precautions, such as satisfying yourself that they are who they say they are and to inform one or two people of where you'll be going, what time you expect to be back, and a general description of who you'll be with in the interim.
If you feel comfortable and happy in the other person's presence and if they reciprocate your feelings, it may proceed to second, third, and more dates during which time your trust in them may build to the extent that you are happy about going to their home alone or inviting them to visit when you're home alone.
Effectively, he's on trial and undergoing assessment all the time - is he a safe driver, do you get the feeling that if you were in an establishment where a fire or fight broke out he'd put your safety before his own, is he courteous and sociable towards others, does he listen to what you say and participate in your conversations without patronising you or dismissing your views - in short, is he someone that you feel you can trust to treat you with respect at all times?
If he fails the various tests of his character, he gets dumped and it's on to the next.
You may have to kiss a load of frogs but eventually you'll find a prince and all the bad times with users, losers, and abusers, will make you appreciate him even more - and it's not a bad thing if you always keep a little bit of your trust and your heart back so that you have something to fall back on if it transpires that, despite your best efforts, you got it wrong again.
As I see no reason why life should be a struggle, I don't wholly subscribe to the maxim of 'no pain, no gain' but sometimes it is an apt adage to decribe the personal growth that comes about through our social interaction and sexual relationships with others.
As the saying has it 'you've got to be in it to win it'. Don't be a loser in life because you failed to get off the starting blocks or didn't recover your momentum when you fell at a hurdle.