Ultimately, no one here can tell you the right answer. But I'll give you my story. I have four kids, 2 of them are biological (if you want more info on that, you can check through my post history). Both of my pregnancies were accidental, and both happened extremely early into those relationships.
The first, my daughter Amy, I conceived her while I was a 17 year old runaway. I'd been with my boyfriend for a couple months, I'd been on the pill, got pregnant anyhow. Being that it wasn't expected, I gave him the chance to back out, and I would just forever say I didn't know who the father was. But my boyfriend told me he'd be there every step of the way. By the time I had her, I'd learned that everything I knew about him was bullshit, a facade. All of his kindness, all of his desire to be a father, everything. Nearly 12 years later, he's still a dopey manchild who flakes out every chance he gets and mostly only comes around when he thinks playing daddy will impress whatever woman he's with. He's also hit on me inappropriately knowing I'm married (while he was married too!). I don't regret my daughter, she's amazing, but I hate that I'm stuck talking to this douchebag forever.
3 years ago, I became pregnant about a month after beginning to date my now-husband. I had been told not too long after I'd had my first baby that due to uterine and hormonal issues that I would never conceive again, that it was miraculous that I'd done it in the first place, and had no reason to doubt that. But life has a way of shaking things up, and there I was, pregnant.
Now with this guy, I had age and maturity and experience under my belt, so I knew from the get-go that he was special, not just a fling. But to bring a kid into it...I had reservations. I gave him the same choice that I gave my boyfriend at 17 - bail now, or buck up and be a dad (I'm pro-choice, but I didn't want to terminate because I knew I may never get this chance again).
We moved in together a couple months later, and had to basically get to know each other while fast-tracking our lives together. And there were times that that was very hard. We've been married about 3 years now, and I wish we'd had that slow time together...dating, going at our own pace. Our "honeymoon" phase had to be cut short with morning sickness and doctor's appointments, and then eventually just the immense pain that came from being massively pregnant with a frickin' huge baby (12lbs, and I'm so grateful for C-sections).
So...yes, it's doable. If this might be the love of your life, then maybe it'll work out, with hard work and sacrifice. However, babies stress and even break well established relationships. My husband and I are lucky that we've seen it through and have no regrets. Seriously, I'm ridiculously in love with him and I melt every time he smiles at me, and I know he's got my back through everything, and I've got his. But this was against the odds.
You won't know how this is going to go down until it does. You have to just ask yourself, are you willing to do this as a single parent? I can tell you firsthand that that's a damned hard road to walk. Amy's father didn't come around until she was 4, and even then it's only half-assedly. When she got pneumonia, it was me who stayed up all night with her and still had to go to work in the morning. When she needed help with homework, it was me. When she had to go to the doctor, it was me. When she started exhibiting severe adhd symptoms, it was me. Always me. No one to take the pressure off. My father helped when he could but understand that that's not the same as having a real partner, a co-parent.
And if he does want to try to be together and be a dad, you have to be prepared for your relationship to change and to survive. You have to establish good communication NOW, not after baby comes. You have to vow - and keep that vow - to give when the other needs, be that time to sleep, emotional support, whatever. And one important thing, for any couple that is having a baby...take time for each other. It's so easy to think only baby, baby, baby, but strong couples make better parents.
You're in a tough spot, but it is what it is. Time to talk it out with your fella and see what his feelings are, and go from there. Once you know where he stands, you'll be in a better position to make your own decisions about the future. Just remember that if you have his baby, you very well may find yourself dealing with him for nearly 20 years. That's not necessarily good or bad, just food for thought. It's time to take a magnifying glass to all his traits, behaviours, his family, etc.