I think you're a bit to late with talking about safe sex.
First of all don't worry about him becoming a teenage father. It's not so bad.
I'd worry about the illnesses he could get.
These days a child won't easily become your end, but STI's sure can make life a lot shorter then you'd like to.
Then second:
For as long as mankind exists we've been having kids around our 15 - 20s.
Since about 60 years ago that all changed.
Our grandparents might still remember the time that when they were 12 they had to work. They were young adults and not like we view them today as children.
We do become older, but we don't stay young any longer then we did.
It's harder to be a teenage parent. It sure is!!!
But not just because of being a teenager, it's the people around you that are going to stare at you.
Think that you can't rise a child, because of your age.
But that's the problem of these people. Try to teach them to look the other way.
Age or money doesn't make anyone a good or a bad parent. If it did then can you explain to me please why I also read in the papers about 40+ parents that neglect their kids? Or children of rich parents who are on drugs?
Maybe try to talk with him about safe sex.
Talk about the STI's.
Tell him also that condoms don't protect against all STI's. For example genital warts and herpes.
Herpes is annoying, but harmless.
Warts can cause in time by a man cancer in and around the penis. For a woman they can cause cervical cancer.
Around 900 woman die every year in the uk of cervical cancer. In 70% of these cases the cancer was caused by a wart virus. That they lady caught during sex. Protected/unprotected.
But how to talk with a teenager about that.. ppfff hard, very hard.
It's not really a child anymore with who you can chat about it in a kids way so they know about it when they grow older.
I can understand he'd not like that kind of chat with you.
Maybe be honest with him. Not about you checking his phone. But that you should have had this kind of chat before.
Give him leaflets about STI's. I think you can get them from your GP or else from a sexual health clique.
Also let him know that you could get free condoms by these clique's and I think also on some other places. They also check you for free on STI's and that you don't need to know anything about it if he doesn't want to.
But if there's anything wrong that he's always welcome to come and have a chat with you.
When he comes and tells you that his girl is pregnant. My advice is to react happy about it. You might be shocked, but just react happy.
They're going to encounter a lot of negativity in these coming months and years. From painful comments to fingers being pointed at them.
They don't need any more negativity from close family. Just be that pillar they can always lean upon no matter what.
Another plus side to that is if you're going to get a grandchild. That because of your positive support you'll also get close to the little one as a grandmother.
That'll be nice, won't it?
A beautiful grand daughter or son.
Think about the lovely trips to the park, Christmas and all the fun moments you'll have with this beautiful little miracle and his/her parents.
(Your son and daughter in law)
Relax, don't make life harder then it already is.
Sylvia