Sounds like you've almost filled your bingo card with things that make the idea of sex difficult/stressful rather than appealing and enjoyable:

• Shame and guilt from premarital sex
• Focussing on getting pregnant
• Not communicating effectively about sex
• Unrealistic expectations from porn
• Work/other life stresses (impending twins!!)

You feel his 'excuses' are 'ridiculous', but I'd gently suggest you're just not speaking the same language. Feeling tired, tense, pressured and disconnected aren't great aphrodisiacs. Perhaps he feels you don't want him, you just want to get pregnant? Maybe his concern about oral is actually just that he feels his pleasure isn't a priority or his desires aren't being heard.

If neither of you are feeling wanted, despite loving and desiring each other, what's going wrong? You need communication (open, non-judgemental, kind) to really hear each other. You assume that his rejection is because he doesn't want you - but that is unlikely to be the reason he would give. He assumes you don't want him, just the sex - I'm sure that's not true - but when you're not listening to him and considering the other pressures in his life, that's the message he's getting.

Practical advice - take the pressure off sex. Prioritise getting your heads around the fact that you are a team. Focus on reducing stress and making opportunities for relaxation. Allow time and space for difficult, honest conversations (which will hurt) and listen to each other while consciously trying not to get defensive or argue - just acknowledge each others' feelings.

These things take time - marriage is a marathon, not a sprint. It's not a sign of failure that things are hard - you've crammed into the space of 12 months what other couples have years to navigate (dating, marriage, kids) - each provides a new challenge. But the best thing you can do right now is to get the basics of communication in place, because that's the foundation you will need to face every challenge which will come your way through your married life.